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Subungual melanoma - Nail and Distal Digit
Other Resources UpToDate PubMed

Subungual melanoma - Nail and Distal Digit

Contributors: Vivian Wong MD, PhD, Susan Burgin MD, Shari Lipner MD, PhD
Other Resources UpToDate PubMed

Synopsis

Nail (subungual) melanoma is a rare subtype of acral lentiginous melanoma that arises in the nail unit due to malignant melanocytic hyperplasia in the nail apparatus. Nail apparatus melanoma is a more frequently represented melanoma in darker skin phototypes, such as individuals of African (15%-20% of all melanomas), American Indian (33%), Hispanic, and Asian (10%-30%) descent, than in individuals of Northern European descent (1%-3%). The diagnosis is challenging and often delayed (average depth at the time of diagnosis is 3.5-4.7 mm). Therefore, it can carry significant mortality and morbidity.

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 Common acquired nevus (benign melanocytic hyperplasia)
  • Focal melanocytic activation
  • Lentigo simplex
  • 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
  • Cutaneous squamous cell carcinoma or Squamous cell carcinoma in situ (Bowen disease)
  • Traumatic Longitudinal melanonychia from repeating trauma, such as nail biting or friction
Polydactylous longitudinal melanonychia:
  • 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 Acrodermatitis continua of Hallopeau
  • 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 disease (HIV)-induced longitudinal melanonychia
  • Nutritional longitudinal melanonychia (eg, Vitamin B12 deficiency 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, Pesticide-induced nail changes), silver nitrate, ethacridine lactate, Tobacco staining of nails, and cosmetics such as henna, Hairdresser, and Nail polish damage

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
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Subungual melanoma - Nail and Distal Digit
A medical illustration showing key findings of Subungual melanoma : Hallux, Hutchinson nail sign, Index finger, Solitary nail or digit, Thumb, Longitudinal erythronychia, Subungual mass, Longitudinal brown-black nail band
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