Nail

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 Author(s): Luc Thomas, Amélie Boespflug
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Description this chapter describes the dermoscopy criteria of nail pigmentation and nail diseases
Author(s) Amélie Boespflug · Luc Thomas
Responsible author Luc Thomas → send e-mail
Status unknown
Status update March 25, 2023
Status by Ralph P. Braun
Subchapter(s): 

Technical aspects for nail dermoscopy

Nail dermoscopy criteria

Tumors

Other nail pigmentations

Algorithm for nail pigmentations


Basic dermoscopical semiology on nails [1][2][3]

Nail plate free edge dermoscopy

Examination of the nail plate free edge permits the observation of subungual localized hyperkeratosis in epithelial tumors of the nail matrix such as Bowen disease, squamous cell carcinoma, onychopapilloma, onychomatricoma and seborrheic keratosis. In onychomatricoma, its remarkable “dotted” free edge surface constitutes another criterion in favor of this diagnosis. In onychopapilloma, the sharp “spine-shaped” hyperkeratotic plug visible underneath the nail plate in the area of nail changes is also very helpful.

Nail plate dermoscopy -oncychomatricoma Nail plate free edge -Onychopapilloma

It is also of interest to dermoscopically examine the distal free edge of the nail plate in cases of melanonychia striata[4] since the position of the pigment in the nail plate gives an interesting indication of the location of the pigmented lesion with the matrix (i.e. proximal versus distal matrix). Since the dorsal aspect of the nail plate is derived from the proximal matrix, the presence of the pigment in the upper part of the nail plate free edge will indicate the site of the causal lesion in the proximal part of the matrix. In contrast, the presence of pigment in the lower part of the nail plate will favor a distal matrix location of the causative lesion. Knowing or estimating the location of a pigmented lesion preoperatively is of tremendous importance in order to inform the patient of the possible esthetic consequences of the biopsy. A biopsy taken from the distal matrix will create a nail plate with an almost invisible defect from underneath whereas a biopsy of the proximal matrix will cause a visible defect of the nail plate surface[5].

Dermoscopy has been used for many years in the differential diagnosis of pigmented skin tumors and has been proven superior to naked-eye examination in the differential diagnosis of melanoma on the skin[6][7]. It therefore seems logical that this technique was first used on the nail unit to better establish the differential diagnosis of nail pigmented longitudinal bands (also known as melanonychia striata). After the publication by Ronger et al. [8], several reports have further analyzed pigmented longitudinal bands of the nail plate. Even though some doubts have been expressed about the real value of dermoscopy of the nail [9], many reports conclude that there is an increased accuracy of diagnosis of nail tumors with dermoscopy compared to the naked eye [10][11][12][13][14][15][16][17][18][19][20].


Blood spots

Blood spots -clinical aspect 185v (1).jpg

Blood spots have a sharp, round-shaped proximal edge and a somewhat filamentous distal edge. Their color varies from purple-red in recent lesions to black-brown in older ones. They are observed in cases of trauma-induced subungual hemorrhages but their diagnosis might be difficult if the trauma was not important enough to be remembered by the patient. This is typically the case with repetitive microtrauma-induced subungual hemorrhages of the toenail due to tight or badly fitting shapes. Blood spots are also observed in malignant tumors of the nail unit and their occurrence can be facilitated by anticoagulation or platelet antiaggregant therapy. Since bleeding can mask the clinical signs of an underlying tumor, reexamination of the patient after 4–6 months (remembering that subungual hemorrhages move distally about two-fold slower than the nail plate itself) is mandatory.

Brown background to the pigmentation

A brown background of the longitudinal band indicates that significant melanocytic hyperplasia exists in the nail matrix. This is observed in nail matrix nevi and pigmented melanomas. The color may vary from light brown to dark brown and even black. The darkness of the color usually reflects the skin type of the patient. Patients with Fitzpatrick’s skin types I, II and IIIa more often show a light brown coloration whereas types IIIb, IV, V and VI show a darker one.

Gray or gray-yellowish background to the pigmentation

Grey background -Clinical Aspect 185l (1).jpg

On dermoscopy of the nail plate, gray color of the band generally indicates that no prominent melanocytic hyperplasia is present in the nail matrix. It is observed in many conditions: lentigo and lentiginoses of various types, ethnic-type pigmentation, drug-induced pigmentation, and repetitive trauma-induced (mostly frictional on toenails) pigmentation. Rarely, it may also be seen in very early cases of in situ melanoma, justifying digital dermoscopy follow-up in doubtful cases. As in the skin, Bowen disease (squamous cell carcinoma in situ) can also be pigmented and in this case the coloration in dermoscopy is often gray rather than black, as also occurs in periungual Bowen disease. In these two latter cases, Bowen disease is regularly monodactylic whereas other conditions generally affect multiple nails.

Regular pattern of parallel micro-lines

Longitudinal pattern of the longitudinal bands 6178b.jpg.jpg

When superimposed over a brown background, thin longitudinal micro-lines can be observed with dermoscopy and when their color, thickness, spacing and parallelism are regular, whatever the depth of their color, which reflects the skin type of the patient, the pattern is called “regular”. This regular pattern is observed in benign melanocytic nevi of the nail matrix.

Irregular pattern of longitudinal parallel micro-lines

Irregular pattern of longitudinal lines -dermoscopic aspect Irregular pattern of the longitudinal lines -dermoscopic aspect

In contrast, when the color, thickness and spacing are irregular and vary from one area to another and when, usually in more advanced cases, areas of disruption of the parallelism are observed, the pattern is called “irregular”. It is the principal dermoscopic symptom of pigmented melanoma and its presence mandates a biopsy of the nail matrix.

Micro Hutchinson’s sign

Micro Hutchinson's sign -Clinical Aspect Micro Hutchinson's sign -Dermoscopic aspect

Clinically Hutchinson’s sign is defined by the pigmentation of the periungual skin around a hyperpigmented nail plate. It is considered a warning sign highly suggestive of melanoma. It is also found in congenital nevi of the nail. It must not be confused with pseudo-Hutchinson’s sign which is visibility of the pigmented band of the nail plate through a translucent cuticle and which has no particular diagnostic significance. With dermoscopy, it is possible to observe very subtle pigmentation of the cuticle or of the submatrix, almost invisible to the naked eye, and called “micro” Hutchinson’s sign. In our experience, this rare sign is almost only observed in melanoma yet might be seen in atypical ethnic-type pigmentation and in congenital nevi of the nail unit.

Atypical Hutchinson’s sign

Atypical Hutchinson sign - Clinical Aspect Atypical Hutchinson's sign -dermoscopic aspect

Atypical Hutchinson’s sign is defined by the presence of at least one of the two major dermoscopic criteria for melanoma in acral sites in the periungual skin: parallel ridge pattern and/or irregular diffuse pigmentation. The parallel ridge pattern is only observed in the anterior aspect of the hands and posterior aspect of the feet distal to Wallace’s line that separates the palmarplantar skin (with fingerprints) from the glabrous skin. It is recognized by the presence of pigment in large parallel bands separated by a thin unpigmented parallel band. Hyperpigmentation of the (large) ridges of the fingerprints contrasting with the (thin) unpigmented furrows was first described in palm and sole melanoma by opposition with the hyperpigmentation of the (thin) furrows contrasting with the hypopigmentation of the (large) ridges that constitutes the hallmark of palm and sole nevi. In cases of nail unit melanoma, irregular diffuse pigmentation is more often found on the supramatricial skin whereas the parallel ridge pattern is only found on the finger/toetip, the pulp of the finger/toe or around the lateral nail folds.

Longitudinal xantholeukonychia

Longitudinal Leuchonychia -Clinical Aspect Longitudinal Leuchonychia -Dermoscopic Aspect

Band-like white coloration of the plate is called leukonychia and yellow coloration called xanthonychia. These two colors are often observed simultaneously within the same lesion.

Band-like longitudinal splinter hemorrhages

Band like splinter Hemmorrhage -Clinical Aspect Band like splinter hemmorrhage -Dermoscopic Aspect

Splinter hemorrhages are found in the nail in many conditions, including connective tissue diseases, onychotillomania, disorders of coagulation or nutrition and hematological disorders. In such cases, they are found on several nails and, on any one nail, involvement is not limited to only a part of the nail plate. When splinter hemorrhages, often in association with other signs such as leukoxanthonychia or polychromia, are limited to a band on the nail plate, an epithelial tumor of the nail matrix should be suspected. Splinter hemorrhages are also often associated with nail unit amelanotic melanoma yet their disposition is less systematized along the plate.

Longitudinal erythronychia with enlarged proximal origin

Longitudinal erythronychia -Clinical Aspect Longitudinal erythronychia -Dermoscopic Aspect

Cherry (senile) hemangiomas of the nail plate are not uncommon and their dermoscopic aspect is, in many cases, characterized as a longitudinal thin erythronychia with a clubbed proximal edge.

Localized subungual hyperkeratosis and distal triangular plate erosion

Nail plate erosion -clinical aspect Distal nail plate erosion -Dermoscopic Aspect

Dermoscopic examination of the free edge of the nail plate at the distal extremity of a longitudinal abnormality, in most cases leukoxanthonychia often with splinter hemorrhages and not uncommonly with polychromia, often shows a localized subungual hyperkeratosis. This often indicates the presence of an epithelial tumor of the nail matrix (onychomatricoma, onychopapilloma, squamous cell carcinoma or seborrheic keratosis). A triangular erosion of the distal nail table indicates the presence of a subungual tumoral syndrome, but the etiology cannot be predicted.

Polychromia

Polychromia -Clinical Aspect Polychromia -Dermoscopic Aspect

Polychromia is defined by the presence of four or more of the following colors: black, red, blue, white, yellow, dark-brown, light-brown, gray or purple. Polychromia is very often observed in malignant amelanotic neoplasms such as squamous cell carcinoma or amelanotic melanoma.

Atypical vessels [21]

In dermoscopy, an atypical pattern of the vessels is defined by at least one of the following criteria :

  • presence of at least three different types of vessels (dots and globules, comma-like, hairpin-like, linear, corkscrew-like, arborizing) within the same lesion
  • presence of linear and irregular vessels (caliber changes from one segment to another of the same vessel)
  • milky-red areas defined as structureless pink areas with various shades of pink without identified vascular structures. These areas are found in pyogenic granuloma and in advanced amelanotic melanoma (the two being impossible to differentiate on the basis of clinical or dermoscopic examination so biopsy for histopathological examination is mandatory).

Yellow spot

Yellow spot -clinical aspect Yellow spot -dermoscopic aspect

A yellow well-demarcated structureless round or ovoid spot is observed in subungual exostosis. It is created by the pressure of the bone on the nail bed tissue underneath a firm plate.

Red spot(s)

Red spots -Clinical aspect Red spots -Dermoscopic aspect


Structureless red spots are observed in areas of nail plate erosion or through the nail plate. Their significance is close to “milky-red areas” and should lead to a biopsy to differentiate amelanotic melanoma from pyogenic granuloma.

Purple-blue spot

Purple spots -Clinical aspect Purple spots -Dermoscopic aspect

A structureless purple or blue spot is observed through the nail plate mainly in two conditions: the extremely rare blue nevus of the nail unit and the very common glomus cell tumor. In the latter, the pressure of the dermoscope on the nail plate can trigger the characteristic “electric” pain of this neoplasm.

Advanced dermoscopy techniques

Nail plate free edge examination

Nail plate free edge dermoscopy

Examination of the nail plate free edge permits the observation of subungual localized hyperkeratosis in epithelial tumors of the nail matrix such as Bowen disease, squamous cell carcinoma, onychopapilloma, onychomatricoma and seborrheic keratosis. In onychomatricoma, its remarkable “dotted” free edge surface constitutes another criterion in favor of this diagnosis. In onychopapilloma, the sharp “spine-shaped” hyperkeratotic plug visible underneath the nail plate in the area of nail changes is also very helpful.


It is also of interest to dermoscopically examine the distal free edge of the nail plate in cases of melanonychia striata[22] since the position of the pigment in the nail plate gives an interesting indication of the location of the pigmented lesion with the matrix (i.e. proximal versus distal matrix). Since the dorsal aspect of the nail plate is derived from the proximal matrix, the presence of the pigment in the upper part of the nail plate free edge will indicate the site of the causal lesion in the proximal part of the matrix. In contrast, the presence of pigment in the lower part of the nail plate will favor a distal matrix location of the causative lesion. Knowing or estimating the location of a pigmented lesion preoperatively is of tremendous importance in order to inform the patient of the possible esthetic consequences of the biopsy. A biopsy taken from the distal matrix will create a nail plate with an almost invisible defect from underneath whereas a biopsy of the proximal matrix will cause a visible defect of the nail plate surface[23].

Intraoperative non-contact polarized light dermoscopy of the nail matrix

Intra-operative dermoscopy

With non-contact polarized light dermoscopy, it is possible to examine the nail matrix during the surgical biopsy procedure without risk of microbial contamination of either the exposed nail matrix or the sterile surgical instruments. In 2005 Hirata et al. proposed the perioperative examination of the nail matrix and described the streaks, pigment network and globules in the nail matrix and nail bed in conditions characterized by nail matrix melanocytic hyperplasia whereas diffuse homogeneous pigmentation was observed in conditions without prominent melanocytic hyperplasia of the nail matrix such as ethnic-type pigmentation[24], [25]. Moreover, we consider that intraoperative dermoscopic examination of the nail bed and the nail matrix permits a more precise targeting of the biopsy than might occur with simple examination using the naked eye. This could also be applied in non-pigmented subungual tumors such as small squamous cell carcinoma, glomus cell tumor[26] onychopapilloma or onychomatricoma[27]. The same authors also proposed ex vivo dermoscopic examination of the nail matrix biopsy. This can be performed with contact immersion dermoscopy and provides much sharper images with similar observations.


We must add that ex vivo reflectance confocal microscopic examination is also possible and allows detailed visualization at the cellular level. Indeed, additional work is badly needed to evaluate ex vivo reflectance confocal microscopic examination of nail matrix pigmented tumors.

Digital dermoscopy follow-up

Digital dermoscopy follow up -Month 0 Digital dermoscopy -Month 4 Digital dermoscopy -10 month follow up


On skin, dermoscopy has been proven efficient (level of proof “A”) to accurately distinguish melanoma from other pigmented lesions but its sensitivity does not reach 100%. For this reason, digital follow-up of high-risk patients and of flat doubtful lesions has been developed. By sequential dermoscopic imaging of the lesion(s) and comparison of images over time, it permits determination of minor changes in shape, color or architecture of a given lesion, to allow an even earlier diagnosis of melanoma than would be possible with classic dermoscopy. Many publications have validated the concept of sequential dermoscopic imaging of cutaneous lesions in order to make a more accurate and precise diagnosis of melanoma (level of proof “B”)[28] but even though the situation appears to be similar for nails, the value of digital sequential imaging of doubtful cases of melanonychia striata has not been yet evaluated in published prospective studies. However, we have some experience with sequential dermoscopy and believe that, in selected indications, digital follow-up of nail pigmentation could help to demonstrate changes over time and therefore aid the diagnosis of suspected melanoma in patients in whom both clinical and dermoscopic criteria are at first insufficient to permit its positive diagnosis. Since the concept has not been established in large series, we will just briefly mention this technique here. However, it is our opinion that prospective large studies are definitively needed to better establish the role and impact of digital dermoscopy follow-up of nail pigmentation.


Nails in Skin of Color

Acral lentiginous melanoma (including the nail unit) is the most common melanoma subtype in black and Asian patients. Melanoma of the nail unit can be difficult to diagnose in persons of color as they are also more likely to have benign nail hyperpigmentation.

Terminology

Longitudinal melanonychia (LM) (also called melanonychia striata) is a pigmented band in the nail plate resulting from melanin deposition. This may result from activation or proliferation of nail matrix melanocytes. Melanocytic proliferation of the nail matrix is caused by nevi and melanoma and melanocytic activation produces ethnic pigmentation and nail lentigo. The nail bed does not normally have melanocytes.

Hyperpigmented nails or LM in persons of color has been given many names:

  • ethnic melanonychia (racial melanonychia)
  • ethnic-type melanonychia
  • ethnic melanosis
  • ethnic hyperpigmentation
  • ethnic pigmentation

In each case the term racial is sometimes used instead of ethnic, but it is our preference to use ethnic as the concept of race can be murky and fraught with bias. The terms benign and nail can also be added to the labels above.

Hutchinson sign is the extension of hyperpigmentation to the nail folds or hyponychial skin as seen in melanoma. Pigmentation in the hyponychial skin may be associated with a parallel ridge pattern on dermoscopy.

Micro-Hutchinson sign is pigmentation of the cuticle that is not visible to the naked eye but visible by dermoscopy. It is very concerning for melanoma when found. It has also been described in congenital nevi in children. Pseudo-Hutchinson sign is the presence of dark pigment around the proximal nail fold secondary to benign conditions such as ethnic melanosis and not melanoma. Another cause of pseudo-Hutchinson sign is a translucent cuticle below which the pigment of LM is visible. Trauma and drug-induced pigmentation can also produce a pseudo-Hutchinson sign.

Epidemiology

Benign nail pigmentation is more common in persons of color. In one study, pigmented bands occurred in 77% of 200 African Americans older than age 20 years. [29] and in almost 100% of those older than age 50 years. [30]

It also occurs in 10% to 20% of persons of Japanese descent. LM is unusual in whites, occurring in only approximately 1% of the population. [31]

Approach to nail lesion diagnosis

2step15.jpg

Causes of nail hyperpigmentation

  • Subungual melanoma and SCC of the nail unit must be considered first.
  • Ethnic melanonychia is due to benign melanocyte activation that often involves several nails and is more common in skin of color. [32]
  • Chronic trauma, especially in the great toes may cause melanocytic activation and nail darkening. It may occur in the fingernails from trauma to the proximal nail fold and cuticle such as in habit tic deformity of the nail.
  • Skin diseases with nail involvement such as psoriasis, lichen planus, amyloidosis, scleroderma and Darier’s disease may result in nail color changes.
  • Drugs causing melanonychia include chemotherapy agents, antimalarials and psoralens. Drug-induced nail pigmentation typically and affects multiple nails.
  • Endocrine disorders, such as Addison disease, Cushing syndrome, hyperthyroidism, and acromegaly, can be responsible for LM.
  • Subungual hematoma/hemorrhage has a distinct dermatoscopic pattern of proximal globules with distal streaks. The color may range from red to brown to black.
  • Nail infections - trichophyton rubrum and some non-dermatophyte molds (particularly Neoscytalidium species) produce pigmented hyphae that can cause green or brown nail discoloration. The cloud-like appearance with dermoscopy can help to make this diagnosis along with KOH, culture or PAS stain.

Subungual hematoma

  • Subungual hematoma with pseudo-Hutchinson sign.

  • Dermoscopy showing distal streaking in a subungual hematoma.


  • Dermoscopy showing proximal globules in a subungual hematoma.


Fungal infection

  • Longitudinal melanonychia. KOH and fungal culture were negative so a nail matrix biopsy was performed showing fungal infection.

  • A fungal infection can cause dark lines in the nails on dermoscopy.


  • Abnormal pigment in the nail plate with cloudlike structures on dermoscopy caused by fungal infection

  • Black pigment in the nail caused by a fungal infection. The cloudlike structures are less visible than in the preceding case. Note that the dark pigment does not go back to the matrix which is reassuring in that melanoma begins in the matrix.

Nail melanoma

In a retrospective observational study performed by the IDS, nail melanoma cases were significantly associated with a pigmented band involving greater than 2/3 the width of the nail plate, grey and black colors, irregularly pigmented lines, Hutchinson and micro-Hutchinson signs, and nail dystrophy. Granular pigmentation was found in 40% of melanomas and only in 3.5% of benign lesions. [33]

Other dermoscopic features of nail melanoma: longitudinal brown to black lines with irregular color, spacing, and thickness. Lines usually show loss of parallelism and may vary within single lines. Other reasons to be concerned for nail melanoma include: abrupt onset of LM after middle age, personal or family history of melanoma, rapid growth, darkening of a melanonychia band, pigment variegation, blurry lateral borders, irregular elevation of the surface, a band width >3 mm, proximal widening, associated nail plate dystrophy, and single rather than multiple digit involvement. [34]


  • Melanoma in-situ in the nail of an African American man. Only one nail is involved and it is clearly more than 2/3 of the nail.

  • Note the presence of a micro-Hutchinson sign (extension of pigment on to the cuticle and proximal nail fold seen best with dermoscopy).

Ethnic pigmentation

  • Hispanic woman with multiple nails showing ethnic pigmentation.

  • The degree of hyperpigmentation may vary between nails in the same individual.

  • Note how the color is grey rather than brown.


  • Ethnic melanonychia involving multiple nails in an African American man with pseudo-Hutchinson sign.

  • Multiple hyperpigmented longitudinal bands are visible with dermoscopy.


  • Ethnic melanonychia in an African American man with pseudo-Hutchinson sign.

  • Dark pigmentation is seen at the proximal nail fold secondary to ethnic melanosis.

Nail nevi

  • Congenital nevus involving the nail of a one-year-old boy.

  • Dermoscopy reveals micro-Hutchinson sign of the cuticle which can be a benign finding in a congenital nevus.

Nail squamous cell carcinoma

  • Squamous cell carcinoma in situ on the nail unit of an African American woman.

  • Note the nail pigmentation and splinter hemorrhages.


  • Note the hyperkeratotic plaque and longitudinal melanonychia.


  • Pigmented squamous cell carcinoma in situ with HPV changes in a 35-year-old Hispanic woman.

  • Note the pigmented lines at the periphery in the top right corner. This mimics the streaks that are seen in melanoma.


Further information on SCC of the nail: SCC (this version)

Nevus and lentigo of the nail matrix

Nevus of the nail matrix

Nail matrix melanocytic acquired nevi are dermoscopically characterized by their brown background coloration and the regular pattern of the longitudinal micro-lines. Congenital nevi may exhibit atypical patterns and their differentiation from melanoma is very difficult on the basis of clinical and dermoscopical features. Therefore careful follow-up is mandatory.

6178a.jpg 6178b.jpg.jpg

Nail unit lentigo or lentiginoses [35][36][37]

Lentigo and lentiginoses of various types (e.g. Laugier–Hutziker, Peutz–Jeghers or Carney complex) may affect the nail unit. Examination of other involved areas and consideration that the nail pigmentation is polydactylic greatly aid in diagnosis. Dermoscopy shows a gray band-like pigmentation. Follow-up of these patients might be difficult since additional longitudinal pigmented bands may occur over time.

Blue nevus of the nail unit

Blue nevus of the nail unit is also a very rare entity[38]. Dermoscopically, it corresponds to a blue proximal spot which is stable over time. In our view, the disease is rare enough to justify surgical exploration of the nail matrix and excision of the lesion.

2195d.jpg 2195b.jpg


Nail unit melanoma in children is extremely rare and very difficult to diagnose [39]. Moreover, unfortunately, clinical as well as dermoscopic criteria used in adults cannot be applied to children since congenital nevi of the nail unit are characterized by signs that are considered extremely suspicious of melanoma in adults[40][41][42][43][44].

Congenital naevus -clinical aspect Congenital naevus -dermoscopic aspect

Triangular shape of the band, irregularity of its pigmentation, nail plate softening or erosion, and periungual pigmentation are very common features of congenital (or congenital-type) nevi of the nail unit. For these reasons, the International Society for Dermoscopy (IDS) has created an international register of congenital and congenital-type nevi of the nail unit. To date, this register has included more than 150 cases worldwide of pigmented lesions of the nail unit either present at birth or diagnosed during the first 5 years of life. This ethical committee-approved register is located in Lyons, France, and held by Lyon 1 Claude Bernard University Dermatology Department. Details for submission of cases can be found on the IDS website[45][46].


Congenital naevus -dermoscopic aspect - Irregular parallèle lines


Since this observational study is still ongoing, we will only include here, with few illustrations, some of our preliminary findings. We commonly determined that an irregular pattern of the dermoscopic longitudinal microlines as well as a triangular shape of the whole band were present in early observations. Periungual involvement, also known as Hutchinson’s sign, was also a very common finding, with a remarkable tropism for the toe/fingertip. The pigmentation in the skin distal to the hyponychium often had a longitudinal and parallel disposition perpendicular to the dermatoglyphics. In rare cases with extremely wide involvement of the periungual skin, a disposition of the pigment along the furrows of the dermatoglyphics, reproducing the classic parallel furrow pattern[47] of benign acral nevi, was observed. We also noticed that a more regular pattern of the pigmentation appeared after a few years of evolution and that, in some cases, the pigmentation faded away almost completely.

Triangular pigmentation

Inclusion of new cases in the register[48] is greatly needed and encouraged in order to increase our knowledge of the natural history of congenital nevi of the nail matrix and to better codify the management of these very difficult cases.


Nail matrix pigmented melanoma

In cases of melanonychia striata in a postpuberty patient, melanoma should be included in the differential diagnosis list[49]. Clinical warning signs are adult onset, monodactylic involvement, changes over time observed by the patient, triangular shape of the band (indicating that the lesion is growing relatively faster than the nail plate), polychromia and the presence of pigmentation of the periungual skin (also known as Hutchinson’s sign). Dermoscopy provides useful additional information: the coloration of the background is light brown to black and the longitudinal dermoscopic micro-lines are irregular in their thickness, spacing and coloration and may show areas of parallelism disruption. Brown-to-black dots and globules may be observed in association with the longitudinal lines. Dermoscopic examination of periungual skin may disclose a micro Hutchinson’s sign invisible to the naked eye. In cases of prominent periungual pigmentation, its dermoscopical features either produce a parallel ridge pattern on the pulp, the lateral aspects and/or distal aspects of the finger/toe or a diffuse irregular pigmentation on the supramatricial skin. Careful attention must be paid to cases in which the irregular pattern of the lines is associated with subungual hemorrhage.

Irregular parrellele micro-lines Irregular parrellele micro-lines

Nail matrix amelanotic melanoma

Amelanotic melanoma of the nail unit is very often a late presentation of the disease after several months/years of the undiagnosed condition which often includes typical monodactylic melanonychia striata[50][51]. At this stage, partial or complete erosion of the nail plate is observed and the pigmentation that the patient eventually recalls having had has vanished, to be replaced by an often exophytic, ulcerative, bleeding tumor. Differential diagnosis includes pyogenic granuloma and several infectious conditions but, as a rule, amelanotic melanoma should be systematically included in cases of monodactylic nail plate erosion with or without nodular and erosive tumor. In this case, dermoscopy reveals features that have been described on amelanotic melanoma of the skin[52].

It shows an atypical vascular pattern characterized by the presence of linear and irregular vessels, the presence of milky-red areas or the presence of three or more types of vessel types within the same lesion. In a few cases, only red spots seen through the nail plate or in areas of plate erosion are visible. It is also possible to identify subtle areas of pigmentation, invisible to the naked eye and incorrectly but traditionally called “remnants” of pigmentation.

512f.JPG.jpg 512l.JPG.jpg


Non Melanoma Nail Tumors

Onychomatricoma

Onychomatricoma exhibits the same dermoscopic features as squamous cell carcinoma but with less architectural disorder and more symmetry, and its demarcation from normal uninvolved nail is sharply delineated. Examination of the free edge of the nail plate can reveal the characteristic punctuations of onychomatricoma. However, in our view, dermoscopic differential diagnosis between onychomatricoma and squamous cell carcinoma (and onychopapilloma) remains difficult[53].

Onychomatricome0023.jpg Onychomatricome0024.jpg


Onychopapilloma

Onychopapilloma is a benign neoplasm of the nail bed and the distal matrix first described by Baran and Perrin1 in 1995[54].

It usually presents itself clinically and dermoscopically as a localized longitudinal band that can have different colors (longitudinal erythronychia[55], longitudinal leukonychia[56], or melanonychia[57]) associated with splinter hemorrhages and a localized distal subungual keratosis[58].


1993c.JPG.jpg Nail plate free edge -Onychopapilloma

Histological examination of an onychopapilloma shows apapillomatous nail bed and distal matrix, associated to layers of hyperkeratosis and matrix metaplasia, and no granular layer[59]


SCC of the nail apparatus

Bowen disease, also known as in situ squamous cell carcinoma[60], can affect the nail and the periungual skin or both, and in rare cases it is polydactylic. Nail involvement can reveal a white-to-yellow longitudinal discoloration of the nail plate but pigmented cases are not uncommon. In the latter case, pigmentation is often grayish rather than brown or black.

Pigmented squamous cell carcinoma.JPG.jpg Per op SCC.JPG.jpg

Other features of epithelial tumors of the matrix may be observed and include band-disposed splinter hemorrhages, polychromia and subungual localized hyperkeratosis.

463e.JPG.jpg 463k.JPG.jpg

Periungual involvement reproduces the dermoscopic features observed in cutaneous Bowen disease: the presence of irregular desquamation, glomerular (round-shaped at classic × 10 or × 20 dermoscopic magnification but exhibiting a tridimensional pattern resembling the glomerulus apparatus of the kidney at higher magnification) vessels grouped in bunches and dust-like gray pigmentation[61].

Invasive squamous cell carcinoma exhibits quite similar but more prominent features[62] with more common bleeding, thicker localized subungual hyperkeratosis and polychromia. In some cases, the lesion is painful and the pain can be triggered by the pressure induced by the dermoscope.

2062b.JPG.jpg 2062l.JPG.jpg


Malignant onychopapilloma.jpg Malignant onychopapilloma free edge.jpg


Malignant onychopapilloma dermoscopy.jpg Malignant onychopapilloma dermoscopy free edge.jpg

Malignant onychopapilloma clinical per op.jpg Malignant onychopapilloma dermoscopy per op.jpg

Glomus-cell tumors

Glomus-cell tumors are rare benign harmatomas of the glomus body, a specialized arteriovenous anastomosis located in the stratum reticularis of the dermis that is involved in thermoregulation[63]. They represent 1-5% of soft tissue tumors of the hand [64] and are mostly located in subungual locations even if they can also rarely appear in extra-digital areas.


Clinically they appear in young adults (20-40 years) as small painful reddish subungual tumefactions. Pain is increased by pressure and by exposure to cold temperatures.


  • Clinical aspect of a clomus-cell tumor

  • Per-operative aspect of a glumos cell tumor after nail avulsion

  • Per-operative aspect of a glomus cell tumor


Nail plate dermoscopy can reveal the presence a structureless purple or blue spot through the nail plate or may find numerous ramifying vessels within a homogeneous red-blue tumor[65],[66].


Dermoscopic aspect of a glomus-cell tumor Dermoscopic aspect glomus-cell tumor


Dermoscopic aspect of a glomus-cell tumor Per-operative dermoscopic aspect of a glomus-cell tumor


Imaging by MRI can help to precise the localization of the tumor and facilitate the pre-surgical evaluation of their size.

MRI glomus-cell tumor aspect


The treatment of glomus-cell tumors consists of a complete surgical removal of the lesion with histological examination. Intra-operative dermoscopy can help delimitate the tumor for an optimal resection, after anesthetic block, the use of a tourniquet (to avoid excessive bleeding) and careful avulsion of the nail plate.


Exostosis

Subungual exostosis (SE) is an isolated acquired slow-growing subungual benign osteo-chondral outgrowth of the dorsal side of the distal phalanx of toes and fingers that is considered by some authors to be a variant of an osteochondroma [67]. In rare cases this outgrowth can be peri-ungual[68].


Subungual exostosis is uncommon even though it is probably underreported[68]. It commonly affects young adults of both genders and is mostly localized on the first right hallux[68]. Reactive metaplasia is believed to be caused by either an acute significant trauma or to minor repeated chronic trauma, and chronic infection [68].


Clinically it appears like an asymptomatic or painful subungual or peri-ungual nodule that uplifts the nail and causes nail dystrophy and onycholysis[68]. Due to its unspecific clinical presentation, accurate diagnosis is often delayed with an average time to diagnosis of 15 months[69].


Dermoscopically, vascular ectasia is the most frequent finding, followed by hyperkeratosis, onycholysis and ulceration. Subungual hyperkeratosis presents itself dermoscopically like a well delimited yellow spot that becomes more visible when pressure is applied by using the dermoscope[70].

Subungual Exostosis.jpg Subungual Exostosis 2.jpg

Differential diagnosis include : subungual warts[71], squamous cell carcinoma, amelanotic subungual melanoma[72], subungual keratoacanthoma, acquired fibrokeratoma, pyogenic granuloma, onychomatricoma and other uncommon subungual nail tumors and bone sarcomas.


The diagnosis is made by performing an X-ray examination that reveals a bony overgrowth. Surgical exploration with total or partial avulsion of the nail and resection of the overgrowth with histological evaluation confirms and treats subungual exostosis[73]. Histopathology typically reveals mature trabecular bone surrounded by a fibrocartilage cap[74]. Incomplete resections expose to the risk of local recurrences [75][76].

Xray of an ungueal exostosis
Per operative aspect of an exostosis
  1. ↑ Ronger S, Touzet S, Ligeron C et al. (2002) Dermoscopic examination of nail pigmentation. Arch Dermatol 138(10): 1327–33.
  2. ↑ Thomas L, Dalle S. (2007) Dermoscopy provides useful information for the management of melanonychia striata. Dermatol Ther 20(1): 3–10.
  3. ↑ Phan A, Dalle S, Touzet S, Ronger-Savlé S, Balme B, Thomas L. (2010) Dermoscopic features of acral lentiginous melanoma in a large series of 110 cases in a white population. Br J Dermatol 162(4): 765–71.
  4. ↑ 28 Braun RP, Baran R, Saurat JH, Thomas L. (2006) Surgical Pearl: dermoscopy of the free edge of the nail to determine the level of nail plate pigmentation and the location of its probable origin in the proximal or distal nail matrix. J Am Acad Dermatol 55(3): 512–13.
  5. ↑ 29 Jellinek N. (2007) Nail matrix biopsy of longitudinal melanonychia: diagnostic algorithm including the matrix shave biopsy. J Am Acad Dermatol 56(5): 803–10.
  6. ↑ 1 Kittler H, Pehamberger H, Wolff K, Binder M. (2002) Diagnostic accuracy of dermoscopy. Lancet Oncol 3(3): 159–65.
  7. ↑ 2 Zalaudek I, Docimo G, Argenziano G. (2009) Using dermoscopic criteria and patient-related factors for the management of pigmented melanocytic nevi. Arch Dermatol 145(7): 816–26.
  8. ↑ 3 Ronger S, Touzet S, Ligeron C et al. (2002) Dermoscopic examination of nail pigmentation. Arch Dermatol 138(10): 1327–33.
  9. ↑ Jellinek NJ. (2010) Dermoscopy between the lines. Arch Dermatol 146(4): 431–3.
  10. ↑ 5 Koga H, Saida T, Uhara H. (2011) Key point in dermoscopic differentiation between early nail apparatus melanoma and benign longitudinal melanonychia. J Dermatol 38(1): 45–52.
  11. ↑ Di Chiacchio N, Hirata SH, Enokihara MY, Michalany NS, Fabbrocini G, Tosti A. (2010) Dermatologists’ accuracy in early diagnosis of melanoma of the nail matrix. Arch Dermatol 146(4): 382–7.
  12. ↑ Phan A, Dalle S, Touzet S, Ronger-Savlé S, Balme B, Thomas L. (2010) Dermoscopic features of acral lentiginous melanoma in a large series of 110 cases in a white population. Br J Dermatol 162(4): 765–71.
  13. ↑ Bilemjian AP, Piñeiro-Maceira J, Barcaui CB, Pereira FB. (2009) Melanonychia: the importance of dermatoscopic examination and of nail matrix/bed observation. An Bras Dermatol 84(2): 185–9.
  14. ↑ Bristow IR, Bowling J. (2009) Dermoscopy as a technique for the early identification of foot melanoma. J Foot Ankle Res 122: 14.
  15. ↑ Tosti A, Piraccini BM, de Farias DC. (2009) Dealing with melanonychia. Semin Cutan Med Surg 28(1): 49–54.
  16. ↑ Thomas L, Dalle S. (2007) Dermoscopy provides useful information for the management of melanonychia striata. Dermatol Ther 20(1): 3–10
  17. ↑ Braun RP, Baran R, Le Gal FA et al. (2007) Diagnosis and management of nail pigmentations. J Am Acad Dermatol 56(5): 835–47
  18. ↑ Tosti A, Argenziano G. (2002) Dermoscopy allows better management of nail pigmentation. Arch Dermatol 138(10): 1369–70.
  19. ↑ Gewirtzman AJ, Saurat JH, Braun RP. (2003) An evaluation of dermoscopy fluids and application techniques. Br J Dermatol 149(1): 59–63.
  20. ↑ Zalaudek I, Kreusch J, Giacomel J, Ferrara G, Catricalà C, Argenziano G. (2010) How to diagnose nonpigmented skin tumors: a review of vascular structures seen with dermoscopy: part I. Melanocytic skin tumors. J Am Acad Dermatol 63(3): 361–74.
  21. ↑ Zalaudek I, Kreusch J, Giacomel J, Ferrara G, Catricalà C, Argenziano G. (2010) How to diagnose nonpigmented skin tumors: a review of vascular structures seen with dermoscopy: part I. Melanocytic skin tumors. J Am Acad Dermatol 63(3): 361–74.
  22. ↑ Braun RP, Baran R, Saurat JH, Thomas L. (2006) Surgical Pearl: dermoscopy of the free edge of the nail to determine the level of nail plate pigmentation and the location of its probable origin in the proximal or distal nail matrix. J Am Acad Dermatol 55(3): 512–13.
  23. ↑ Jellinek N. (2007) Nail matrix biopsy of longitudinal melanonychia: diagnostic algorithm including the matrix shave biopsy. J Am Acad Dermatol 56(5): 803–10.
  24. ↑ Hirata SH, Yamada S, Almeida FA et al. (2006) Dermoscopic examination of the nail bed and matrix. Int J Dermatol 45(1): 28–30
  25. ↑ Hirata SH, Yamada S, Almeida FA et al. (2005) Dermoscopy of the nail bed and matrix to assess melanonychia striata. J Am Acad Dermatol 53(5): 884–6.
  26. ↑ Rai AK Role of intraoperative dermoscopy in excision of nail unit glomus tumor. Indian Dermatol Online J. 2016 Sep-Oct;7(5):448-450
  27. ↑ E. Ginoux, M. Perier Muzet, N. Poulalhon, S. Debarbieux, S. Dalle and L. Thomas Intraoperative dermoscopic features of onychomatricoma: a review of 10 cases in press clin exp dermatology 2017
  28. ↑ Altamura D, Avramidis M, Menzies SW. (2008) Assessment of the optimal interval for and sensitivity of short-term sequential digital dermoscopy monitoring for the diagnosis of melanoma. Arch Dermatol 144(4): 502–6.
  29. ↑ Leyden et al.: Diffuse and banded melanin pigmentation in nails. Arch Dermatol 1972;105:548-50. PMID: 5017264.
  30. ↑ Ruben: Pigmented lesions of the nail unit: clinical and histopathologic features. Semin Cutan Med Surg 2010;29:148-58. PMID: 21051008. DOI.
  31. ↑ Baran & Kechijian: Longitudinal melanonychia (melanonychia striata): diagnosis and management. J Am Acad Dermatol 1989;21:1165-75. PMID: 2685057. DOI.
  32. ↑ Astur et al.: Reassessing Melanonychia Striata in Phototypes IV, V, and VI Patients. Dermatol Surg 2016;42:183-90. PMID: 26845538. DOI.
  33. ↑ Benati et al.: Clinical and dermoscopic clues to differentiate pigmented nail bands: an International Dermoscopy Society study. J Eur Acad Dermatol Venereol 2017;31:732-736. PMID: 27696528. DOI.
  34. ↑ Leung et al.: Melanonychia striata: clarifying behind the Black Curtain. A review on clinical evaluation and management of the 21st century. Int J Dermatol 2019;58:1239-1245. PMID: 31006857. DOI.
  35. ↑ Ronger S, Touzet S, Ligeron C et al. (2002) Dermoscopic examination of nail pigmentation. Arch Dermatol 138(10): 1327–33
  36. ↑ Sendagorta E, Feito M, Ramírez P, Gonzalez-Beato M, Saida T, Pizarro A. (2010) Dermoscopic findings and histological correlation of the acral volar pigmented maculae in Laugier–Hunziker syndrome. J Dermatol 37(11): 980–4.
  37. ↑ Gencoglan G, Gerceker-Turk B, Kilinc-Karaarslan I, Akalin T, Ozdemir F. (2007) Dermoscopic findings in Laugier–Hunziker syndrome. Arch Dermatol 143(5): 631–3.
  38. ↑ Causeret AS, Skowron F, Viallard AM, Balme B, Thomas L. (2003) Subungual blue nevus. J Am Acad Dermatol 49(2): 310–12.
  39. ↑ Altamura D, Avramidis M, Menzies SW. (2008) Assessment of the optimal interval for and sensitivity of short-term sequential digital dermoscopy monitoring for the diagnosis of melanoma. Arch Dermatol 144(4): 502–6.
  40. ↑ Iorizzo M, Tosti A, Di Chiacchio N et al. (2008) Nail melanoma in children: differential diagnosis and management. Dermatol Surg 34(7): 974–8.
  41. ↑ Richert B, André J. (2011) Nail disorders in children: diagnosis and management. Am J Clin Dermatol 12(2): 101–12.
  42. ↑ Léauté-Labrèze C, Bioulac-Sage P, Taïeb A. (1996) Longitudinal melanonychia in children. A study of eight cases. Arch Dermatol 132(2): 167–9. Erratum in: Arch Dermatol 132(9): 112.
  43. ↑ Wong DE, Brodkin RH, Rickert RR, McFalls SG. (1991) Congenital melanonychia. Int J Dermatol 30(4): 278–80
  44. ↑ Coskey RJ, Magnell TD, Bernacki EG Jr. (1983) Congenital subungual nevus. J Am Acad Dermatol 9(5): 747–51.
  45. ↑ Caron GA. (1962) Familial congenital pigmented naevi of the nails. Lancet 1(7228): 508–9.
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  48. ↑ Caron GA. (1962) Familial congenital pigmented naevi of the nails. Lancet 1(7228): 508–9.
  49. ↑ Tosti A, Piraccini BM, de Farias DC. (2009) Dealing with melanonychia. Semin Cutan Med Surg 28(1): 49–54.
  50. ↑ Phan A, Touzet S, Dalle S, Ronger-Savlé S, Balme B, Thomas L. (2006) Acral lentiginous melanoma: a clinicoprognostic study of 126 cases. Br J Dermatol 155(3): 561–9.
  51. ↑ Phan A, Touzet S, Dalle S, Ronger-Savlé S, Balme B, Thomas L. (2007) Acral lentiginous melanoma: histopathological prognostic features of 121 cases. Br J Dermatol 157(2): 311–18.
  52. ↑ Zalaudek I, Kreusch J, Giacomel J, Ferrara G, Catricalà C, Argenziano G. (2010) How to diagnose nonpigmented skin tumors: a review of vascular structures seen with dermoscopy: part I. Melanocytic skin tumors. J Am Acad Dermatol 63(3): 361–74.
  53. ↑ Lesort C, Debarbieux S, Duru G, Dalle S, Poulhalon N, Thomas L. Dermoscopic Features of Onychomatricoma: A Study of 34 Cases. Dermatology. 2015;231(2):177-83
  54. ↑ R. Baran, C. Perrin Localized multinucleate distal subungual keratosis Br J Dermatol, 133 (1) (1995), pp. 77-82
  55. ↑ R. Baran, R. Perrin Longitudinal erythronychia with distal subungual keratosis: onychopapilloma of the nail bed and Bowen's disease Br J Dermatol, 143 (1) (2000), pp. 132-135
  56. ↑ V. Criscione, G. Telang, N.J. Jellinek Onychopapilloma presenting as longitudinal leukonychia J Am Acad Dermatol, 63 (3) (2010), pp. 541-542
  57. ↑ M. Miteva, P.A. Fanti, P. Romanelli, M. Zaiac, A. Tosti Onychopapilloma presenting as longitudinal melanonychia J Am Acad Dermatol, 66 (6) (2012), pp. e242-e243
  58. ↑ J Am Acad Dermatol. 2016 Mar;74(3):521-6. doi: 10.1016/j.jaad.2015.08.053. Epub 2015 Oct 27. Clinical, dermoscopic, and pathologic features of onychopapilloma: A review of 47 cases. Tosti A1, Schneider SL2, Ramirez-Quizon MN3, Zaiac M4, Miteva M5.
  59. ↑ R. Baran, R. Perrin Longitudinal erythronychia with distal subungual keratosis: onychopapilloma of the nail bed and Bowen's disease Br J Dermatol, 143 (1) (2000), pp. 132-135
  60. ↑ Dalle S, Depape L, Phan A, Balme B, Ronger-Savlé S, Thomas L. (2007) Squamous cell carcinoma of the nail apparatus: clinicopathological study of 35 cases. Br J Dermatol 156(5): 871–4.
  61. ↑ Zalaudek I, Argenziano G, Leinweber B et al. (2004) Dermoscopy of Bowen’s disease. Br J Dermatol 150(6): 1112–16.
  62. ↑ Cogrel O, Beylot-Barry M, Doutre MS. (2008) Subungual squamous cell carcinoma revealed by longitudinal erythronychia. Ann Dermatol Venereol 135(12): 883–5.
  63. ↑ Goldblum JR, Folpe AL, Weiss SW. Perivascular tumours. In: Goldblum JR, Folpe AL, Weiss SW, editors. Enzinger and Weiss’s soft tissue tumours. 6th ed. Philadelphia: Elsevier; 2014. p. 749-65.
  64. ↑ Soule EH, Ghormley RK, Bulbulian AH. Primary tumors of the soft tissues of the extremities exclusive of epithelial tumors: an analysis of five hundred consecutive cases. AMA Arch Surg 1955;70:462- 74.
  65. ↑ Maehara LS, Ohe EM, Enokihara MY, et al. Diagnosis of glomus tumor by nail bed and matrix dermoscopy. An Bras Dermatol. 2010;85:236-238. 43. Haenssle HA, Blum A, Hofmann-Wellenhof R, et al.
  66. ↑ When all you have is a dermatoscope- start looking at the nails. Dermatol Pract Concept. 2014;4:11-20.
  67. ↑ Russell JD, Nance K, Nunley JR, Maher IA. Subungual exostosis. Cutis 2016;98:128–9.
  68. ↑ 68.0 68.1 68.2 68.3 68.4 DaCambra MP, Gupta SK, Ferri-de-Barros F. Subungual exostosis of the toes: a systematic review. Clinical Orthopaedics and Related Research 2014;472:1251–9.
  69. ↑ Piccolo V, Argenziano G, Alessandrini AM, Russo T, Starace M, Piraccini BM. Dermoscopy of Subungual Exostosis A Retrospective Study of 10 Patients Dermatology 2017;233:80–5
  70. ↑ Thomas L, Vaudaine M, Wortsman X, Jemec G, Drapé J. Imaging the nail unit. In: Thomas L, Baran R, editors. Baran and Dawber’s Diseases of the Nails and Their Management,. 4rth ed., London: Wiley Blackwell; 2012, p. 111–82.
  71. ↑ Daragad M, Srinivas S, Varghese J. Exostosis masquerading as a subungual wart. Indian Dermatology Online Journal 2014;5:92.
  72. ↑ Velanovich V. Subungual pigmented lesion caused by a bone spur: a mimic of a subungual melanoma. Military Medicine 1994;159:663.
  73. ↑ Basar H, Bal E, Inanmaz M, Basar B, Köse K. Protruded and nonprotruded subungual exostosis: Differences in surgical approach. Indian Journal of Orthopaedics 2014;48:49.
  74. ↑ Russell JD, Nance K, Nunley JR, Maher IA. Subungual exostosis. Cutis 2016;98:128–9.
  75. ↑ Wollina U, Baran R, Schönlebe J. Dystrophy of the Great Toenail by Subungual Exostosis and Hyperostosis: Three Case Reports with Different Clinical Presentations. Skin Appendage Disorders 2016;1:213–6.
  76. ↑ Malkoc M, Korkmaz O, Keskinbora M, Seker A, Oltulu I, Bulbul AM, et al. Surgical treatment of nail bed subungual exostosis. Singapore Medical Journal 2016;57:630–3.
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