Subungual melanoma - Nail and Distal Digit
Alerts and Notices
Synopsis
The vast majority of nail melanomas arise in the nail matrix. Melanoma arising from the nail bed is rare. Two-thirds of cases of nail melanoma present as longitudinal melanonychia. More advanced cases present as a subungual mass with associated onychodystrophy. Hutchinson's sign (extension of pigment to the nail folds) is another sign of advanced nail melanoma. Some subungual melanoma cases are amelanotic (nonpigmented), making early diagnosis even more difficult.
The thumb is the most frequently involved digit, followed by the hallux and then index finger. Subungual melanoma most commonly affects adults in the fifth to seventh decades. There is no male or female predilection.
Nail melanoma is exceedingly rare in children. The majority of pediatric cases occur in children with darker skin phototypes. Similar to their adult counterparts, pediatric cases often present as longitudinal melanonychia.
Codes
ICD10CM:D03.9 – Melanoma in situ, unspecified
SNOMEDCT:
403927001 – Malignant melanoma of nail apparatus
Look For
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
Monodactylous band of melanonychia:- Nail matrix nevi (benign melanocytic hyperplasia)
- Focal melanocytic activation
- Nail lentigo
- Subungual hematoma (however, note that bleeding does not rule out an underlying melanoma)
- Onychomycosis – longitudinal melanonychia may occur in concert with other typical findings
- Onychopapilloma
- Squamous cell carcinoma or squamous cell carcinoma in situ (Bowen disease)
- Traumatic longitudinal melanonychia from repeating trauma, such as nail biting or friction
- Normal pigmentation in darker skin phototypes
- Traumatic longitudinal melanonychia from repeating trauma, such as nail biting or friction
- Longitudinal melanonychia associated with inflammatory nail disorders, such as lichen planus, onychomycosis, chronic radiodermatitis, pustular psoriasis, or Hallopeau disease
- Medication-induced longitudinal melanonychia from minocycline, psoralens, zidovudine, cyclophosphamide (drug-induced nail pigment)
- Radiation-induced longitudinal melanonychia (see radiation dermatitis)
- Melanin deposition due to various conditions, including argyria, Addison disease, porphyria
- Human immunodeficiency virus (HIV)-induced longitudinal melanonychia
- Nutritional longitudinal melanonychia (eg, vitamin B12 or folate deficiency)
- Laugier-Hunziker syndrome – benign pigmentary condition with lentigines (buccal mucosa, lips, gums, tongue, palate, neck, abdomen, genitalia, fingers, toes) and longitudinal melanonychia
- Subungual hematoma
- Exogenous pigmentation of the nail plate from various causes, including chemicals (eg, pesticides), silver nitrate, ethacridine lactate, tobacco, and cosmetics such as henna, hair dyes, and nail polish residue
Best Tests
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Management Pearls
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Therapy
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References
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Last Reviewed:03/28/2019
Last Updated:11/04/2020
Last Updated:11/04/2020
Subungual melanoma - Nail and Distal Digit