Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

Subungual melanoma — melanoma arising beneath the nail — accounts for approximately 2% of melanomas in Caucasian populations but up to 20–30% of melanomas in darker-skinned individuals. Its location beneath the nail creates a diagnostic challenge that frequently delays definitive diagnosis by 1–2 years, contributing to its disproportionate mortality compared to cutaneous melanoma of similar thickness. Every podiatric physician must be able to identify the clinical signs of subungual melanoma and apply the ABCDEF criteria for nail pigmentation to determine which lesions require urgent dermatology referral and nail biopsy.

Longitudinal Melanonychia: The Clinical Presentation

Subungual melanoma typically presents as longitudinal melanonychia — a brown, black, or grey band running the length of the nail from the lunula to the distal nail edge, produced by melanin deposition from a subungual lesion. It most commonly involves the thumb, hallux (most common toe location), and index finger. The clinical challenge is that longitudinal melanonychia is far more commonly caused by benign conditions — nail matrix nevi, ethnic melanonychia (normal in darker-skinned individuals — up to 75% of African Americans over age 50), medication-induced pigmentation (hydroxyurea, doxorubicin), and inflammatory nail conditions — than by melanoma. The critical skill is distinguishing benign from suspicious melanonychia.

ABCDEF Criteria for Nail Pigmentation

A standardized criteria set guides the evaluation: A — Age and ethnicity (fifth through seventh decades; African, Native American, or Asian ancestry — higher risk); B — Brown or Black band with Blurred borders (irregular margins of the pigmented band); C — Change in the band (rapid color change, width increase, or new satellite pigmentation); D — Digit most commonly involved (thumb, hallux, index finger); E — Extension of pigmentation onto the proximal or lateral nail fold (Hutchinson’s sign — pathognomonic for subungual melanoma when true rather than pseudo-Hutchinson’s); F — Family or personal history of melanoma. Any single criterion of B (black band with blurred borders), C (rapid change), or E (true Hutchinson’s sign) warrants urgent dermatology referral and nail matrix biopsy. Hutchinson’s sign — periungual pigmentation extending from the nail onto the proximal or lateral nail fold — is the single most important clinical finding and should always trigger immediate specialist evaluation. Nail matrix biopsy with appropriate technique (3mm punch or excisional biopsy through the nail) provides histological diagnosis. Dr. Biernacki at Balance Foot & Ankle evaluates suspicious nail pigmentation at toenail examination visits. Any hallux or toe nail stripe with concerning features prompts immediate referral. Call (810) 206-1402 for nail evaluation.

Comprehensive Nail Health Guide

The toenails are a window into your overall health. Changes in nail color, thickness, texture, or growth rate can signal local infection, systemic disease, or nutritional deficiency.

Common Nail Problems and Their Causes

• Thickened nails: Usually fungal infection (onychomycosis), but also trauma or psoriasis
• Yellow/brown nails: Fungal infection most common; also smoking, nail polish staining
• Vertical ridges: Normal aging; also low iron, B12 deficiency
• Horizontal ridges (Beau’s lines): Indicate systemic illness or nail trauma
• White spots: Usually minor trauma; less commonly zinc deficiency
• Spoon-shaped nails (koilonychia): Iron deficiency anemia
• Clubbing: Requires evaluation for heart or lung disease

Learn more about toenail fungus treatment and ingrown toenail treatment at Balance Foot & Ankle.

Nail & Skin Cancer Screening at Balance Foot & Ankle

Subungual melanoma — melanoma under the toenail — is rare but deadly if missed. Any dark streak, band, or discoloration under a toenail that changes should be evaluated promptly. Our podiatrists perform thorough skin and nail cancer screenings.

Schedule a Nail Assessment → | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Levit EK, Kagen MH, Scher RK. “The ABC Rule for Clinical Detection of Subungual Melanoma.” Journal of the American Academy of Dermatology. 2000;42(2):269-274.
2. Tan KB, et al. “Subungual Melanoma: A Study of 124 Cases Highlighting Features of Early Lesions.” British Journal of Dermatology. 2007;156(6):1300-1307.
3. Braun RP, et al. “Diagnosis and Treatment of Nail Pigmentations.” Journal of the American Academy of Dermatology. 2007;56(5):835-847.

Your Board-Certified Podiatrists

Dr. Tom Biernacki, DPM

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Dr. Tom Biernacki, DPM

Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.