Basic nail dermoscopy criteria
This chapter describes all dermoscopy criteria of nail dermoscopy
It has the following subchapters:
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[1][2]. 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. [3], 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 [4], many reports conclude that there is an increased accuracy of diagnosis of nail tumors with dermoscopy compared to the naked eye [5][6][7][8][9][10][11][12][13][14][15].
Basic dermoscopical semiology on nails [16][17][18]
Blood spots
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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
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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
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
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
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’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
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
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
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
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 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 [19]
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
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)
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
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
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[20] 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[21].
Intraoperative non-contact polarized light dermoscopy of the nail matrix
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[22], [23]. 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[24] onychopapilloma or onychomatricoma[25]. 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
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”)[26] 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.
- ↑ 1 Kittler H, Pehamberger H, Wolff K, Binder M. (2002) Diagnostic accuracy of dermoscopy. Lancet Oncol 3(3): 159–65.
- ↑ 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.
- ↑ 3 Ronger S, Touzet S, Ligeron C et al. (2002) Dermoscopic examination of nail pigmentation. Arch Dermatol 138(10): 1327–33.
- ↑ Jellinek NJ. (2010) Dermoscopy between the lines. Arch Dermatol 146(4): 431–3.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Bristow IR, Bowling J. (2009) Dermoscopy as a technique for the early identification of foot melanoma. J Foot Ankle Res 122: 14.
- ↑ Tosti A, Piraccini BM, de Farias DC. (2009) Dealing with melanonychia. Semin Cutan Med Surg 28(1): 49–54.
- ↑ Thomas L, Dalle S. (2007) Dermoscopy provides useful information for the management of melanonychia striata. Dermatol Ther 20(1): 3–10
- ↑ Braun RP, Baran R, Le Gal FA et al. (2007) Diagnosis and management of nail pigmentations. J Am Acad Dermatol 56(5): 835–47
- ↑ Tosti A, Argenziano G. (2002) Dermoscopy allows better management of nail pigmentation. Arch Dermatol 138(10): 1369–70.
- ↑ Gewirtzman AJ, Saurat JH, Braun RP. (2003) An evaluation of dermoscopy fluids and application techniques. Br J Dermatol 149(1): 59–63.
- ↑ 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.
- ↑ Ronger S, Touzet S, Ligeron C et al. (2002) Dermoscopic examination of nail pigmentation. Arch Dermatol 138(10): 1327–33.
- ↑ Thomas L, Dalle S. (2007) Dermoscopy provides useful information for the management of melanonychia striata. Dermatol Ther 20(1): 3–10.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Jellinek N. (2007) Nail matrix biopsy of longitudinal melanonychia: diagnostic algorithm including the matrix shave biopsy. J Am Acad Dermatol 56(5): 803–10.
- ↑ Hirata SH, Yamada S, Almeida FA et al. (2006) Dermoscopic examination of the nail bed and matrix. Int J Dermatol 45(1): 28–30
- ↑ 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.
- ↑ Rai AK Role of intraoperative dermoscopy in excision of nail unit glomus tumor. Indian Dermatol Online J. 2016 Sep-Oct;7(5):448-450
- ↑ 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
- ↑ 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.
