Lesions in special locations in skin of color
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. [1] and in almost 100% of those older than age 50 years. [2]
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. [3]
Approach to nail lesion diagnosis
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. [4]
- 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. [5]
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. [6]
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)
Oral Mucosa
Dermoscopy of mucous membranes has been named mucoscopy. At this time there are no studies that compare dermoscopy of mucous membranes from persons of color with persons of lighter skin. In fact, the literature on mucoscopy is small due to the fact that melanomas are rare on mucous membranes such as the lips, oral mucosa and anogenital regions. While squamous cell carcinoma is more common than melanoma in these regions due to HPV, there is still little written on the dermoscopy of these lesions. We will review some of the existing literature and present examples from our practice and the chapter on mucous membranes in the general area of Dermoscopedia.
In one study, benign pigmented lesions of the mucocutaneous junction and mucous membranes presented with:
- dotted-globular pattern (25%)
- homogeneous pattern (25%)
- fish scale-like pattern (18.8%)
- hyphal pattern (18.8%)
- (note the fish scale-like pattern and hyphal pattern are considered to be variants of the ring-like pattern)
Melanomas of these sites showed:
- multicomponent pattern (75%)
- homogeneous pattern (25%) [7]
In a multicenter study by the International Dermoscopy Society (IDS), the combination of blue, gray, or white color with structureless zones are the strongest indicators of malignant mucosal lesions in dermoscopy. [8]
Labial melanotic macules
Middle-aged Hispanic man with labial melanotic macule.
Note the dots, globules, and parallel lines on dermoscopy.
Middle-aged Hispanic man with labial melanotic macule.
Note the fish-scale pattern on dermoscopy.
Young Hispanic woman with labial melanotic macule.
Note the homogeneous structureless pattern on dermoscopy.
Squamous cell carcinoma of the lip
Squamous cell carcinoma of the lip and 71-year-old Hispanic man.
Dermoscopy reveals brown dots in a vertical linear arrangement along with white plaques.
Melanoma of the lip
Melanoma of the upper mucosal lip.
Dermoscopy allows for better appreciation of the blue, white, and brown areas within this mucosal melanoma.
Genital Mucosa
Benign genital
Benign nevus on the glans penis in a young Hispanic male. This was new and growing, so biopsy was performed to rule out melanoma.
Dermoscopy reveals dots and globules.
A retrospective dermoscopic study was conducted on 87 genital lesions with histopathologically proven benign melanosis.[9] The patterns found were:
- ring-like pattern (32%) characterized by multiple round to oval structures, white to tan, with dark brown, well-defined regular borders
- structureless and globular-like patterns (21%)
- parallel pattern (17%)
- cobblestone-like and reticular-like patterns (5%)
The ring-like pattern was frequently associated with multifocality and simultaneous occurrence at the labia majora and the labia minora.
Benign genital melanosis.
Dermoscopy shows a structureless pattern with subtly variegated brown pigmentation.
Benign genital melanosis.
Dermoscopy reveals a structureless pattern characterized by homogenous dark brown pigmentation.
Benign genital melanosis.
Dermoscopy shows both structureless and globular-like pattern with aggregated round to oval brown structures.
Benign genital melanosis.
Dermoscopy reveals a globular-like pattern with small aggregated dark brown structures.
Bowen’s genital
Pigmented Bowen’s disease involving the labia and perineum.
Dermoscopy shows structureless pattern consisting of multiple colors with blue-grey centrally and brown at the periphery.
Genital melanoma
Photographs from: Andreas Blum, Olga Simionescu
Mucosal melanoma of the vulva.
Dark brown homogenous pigmentation with focal white areas centrally.
A great summary chart from the Mucosa chapter in Dermoscopedia by Andreas Blum, Olga Simionescu:
| Pattern | Aspect | Signal for |
|---|---|---|
| Parallel pattern | The pigmentation is linearly distributed (wispy linear streaks) | Vulvar melanosis, in focal areas of mucosal melanoma, pigmented warts |
| Structureless (homogenous) pattern | Diffuse light to dark brown, black, grey-blue pigmented or white areas devoid of any visible structures. In white structures polymorphic vessels could be visible | Highly suggestive for melanoma, mainly in elderly people |
| Reticular pattern | Honeycomb pattern of pigmented network | |
| Dotted globular pattern | Dots and globules | Melanocytic lesions Bowenoid papulosis |
| Ring-like pattern | Do not form a complete circle (“fish scale like structures”) | Melanosis |
Links to additional chapters on Skin of Color
References
- ↑ Leyden et al.: Diffuse and banded melanin pigmentation in nails. Arch Dermatol 1972;105:548-50. PMID: 5017264.
- ↑ Ruben: Pigmented lesions of the nail unit: clinical and histopathologic features. Semin Cutan Med Surg 2010;29:148-58. PMID: 21051008. DOI.
- ↑ Baran & Kechijian: Longitudinal melanonychia (melanonychia striata): diagnosis and management. J Am Acad Dermatol 1989;21:1165-75. PMID: 2685057. DOI.
- ↑ Astur et al.: Reassessing Melanonychia Striata in Phototypes IV, V, and VI Patients. Dermatol Surg 2016;42:183-90. PMID: 26845538. DOI.
- ↑ 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.
- ↑ 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.
- ↑ Lin et al.: Dermoscopy of pigmented lesions on mucocutaneous junction and mucous membrane. Br J Dermatol 2009;161:1255-61. PMID: 19673880. DOI.
- ↑ Blum et al.: Dermoscopy of pigmented lesions of the mucosa and the mucocutaneous junction: results of a multicenter study by the International Dermoscopy Society (IDS). Arch Dermatol 2011;147:1181-7. PMID: 21680757. DOI.
- ↑ Ferrari et al.: The ringlike pattern in vulvar melanosis: a new dermoscopic clue for diagnosis. Arch Dermatol 2008;144:1030-4. PMID: 18711077. DOI.
