Lesions in special locations in skin of color

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Main PageSkin of colorLesions in special locations in skin of color
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Description This chapter describes the dermoscopy criteria in skin of color
Author(s) Jordan Abbott · Rachel Manci · Richard Usatine
Responsible author Richard Usatine→ send e-mail
Status open
Status update July 19, 2023
Status by Ralph P. Braun

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.


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.


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

Fungal infection

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]

Ethnic pigmentation

Nail nevi

Nail squamous cell carcinoma

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

Squamous cell carcinoma of the lip

Melanoma of the lip

Genital Mucosa

Benign genital

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.

Bowen’s genital

Genital melanoma

Photographs from: Andreas Blum, Olga Simionescu

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


  1. Leyden et al.: Diffuse and banded melanin pigmentation in nails. Arch Dermatol 1972;105:548-50. PMID: 5017264.
  2. Ruben: Pigmented lesions of the nail unit: clinical and histopathologic features. Semin Cutan Med Surg 2010;29:148-58. PMID: 21051008. DOI.
  3. Baran & Kechijian: Longitudinal melanonychia (melanonychia striata): diagnosis and management. J Am Acad Dermatol 1989;21:1165-75. PMID: 2685057. DOI.
  4. Astur et al.: Reassessing Melanonychia Striata in Phototypes IV, V, and VI Patients. Dermatol Surg 2016;42:183-90. PMID: 26845538. DOI.
  5. 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.
  6. 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.
  7. Lin et al.: Dermoscopy of pigmented lesions on mucocutaneous junction and mucous membrane. Br J Dermatol 2009;161:1255-61. PMID: 19673880. DOI.
  8. 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.
  9. Ferrari et al.: The ringlike pattern in vulvar melanosis: a new dermoscopic clue for diagnosis. Arch Dermatol 2008;144:1030-4. PMID: 18711077. DOI.
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