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

What Is Subungual Melanoma?

Subungual melanoma is a rare but aggressive form of melanoma arising from the melanocytes in the nail matrix — the tissue beneath the proximal nail fold that produces the nail plate. Unlike sun-exposure-related melanomas elsewhere on the body, subungual melanoma is not associated with UV radiation and occurs at equal rates regardless of skin pigment. This means it affects people of all races and ethnicities, though it represents a disproportionately higher percentage of melanomas in darker-skinned populations simply because other melanoma subtypes are less common in those groups.

The great toe is the most commonly affected digit, accounting for 60-75% of subungual melanomas on the foot. The nail plate initially shows a longitudinal melanonychia — a pigmented streak running from the nail base to the free edge. As the melanoma progresses, the streak widens, becomes irregular in color and borders, and may eventually destroy the nail plate entirely. Advanced lesions ulcerate, bleed, and can invade the underlying bone (distal phalanx).

The prognosis for subungual melanoma is significantly worse than for cutaneous melanoma of equivalent thickness — 5-year survival rates of 50-60% compared to 80-90% for general melanoma. This disparity is almost entirely attributable to delayed diagnosis. A 2024 meta-analysis in the Journal of the American Academy of Dermatology found that the average Breslow thickness at diagnosis for subungual melanoma was 3.1mm (Stage IIB or higher) compared to 0.9mm for general cutaneous melanoma — a difference that represents months to years of undetected growth.

Warning Signs: The ABCDEFs of Nail Melanoma

The ABCDEF system helps identify suspicious nail pigmentation: A (Age) — peak incidence 50-70 years; African American, Asian, and Native American ancestry have higher proportional rates. B (Band) — brown or black longitudinal band in the nail, especially if wider than 3mm, dark brown/black, or with blurred/irregular borders. C (Change) — any change in an existing nail band, including widening, darkening, or irregular color variation. D (Digit) — the great toe and thumb are most commonly affected.

E (Extension of pigment) — Hutchinson sign: pigmentation spreading from the nail bed onto the surrounding skin of the nail fold (cuticle area). This is the single most important clinical indicator of subungual melanoma and demands immediate biopsy. When pigment extends beyond the nail plate onto the periungual skin, the probability of melanoma exceeds 75% in some series. Even subtle Hutchinson sign — visible only with dermatoscopy — warrants tissue sampling.

F (Family history) — personal or family history of melanoma increases suspicion. Additional concerning features include nail destruction or dystrophy with pigmentation, bleeding from the nail bed without clear traumatic cause, a pigmented band that appears suddenly in a previously normal nail (especially in adults over 50), and failure of a previously attributed subungual hematoma to grow out with the nail over 6-8 weeks. A true subungual hematoma migrates distally as the nail grows; pigment that remains fixed at the proximal nail fold is not a hematoma and needs evaluation.

Diagnosis: When and How to Biopsy

Any longitudinal melanonychia (pigmented nail band) meeting one or more ABCDEF criteria should be biopsied rather than monitored. The traditional approach of “watchful waiting” has been largely abandoned for suspicious nail lesions because the cost of delayed diagnosis — advanced-stage melanoma — far exceeds the morbidity of a diagnostic nail matrix biopsy. Dr. Tom Biernacki maintains a low threshold for biopsy of any pigmented nail lesion that cannot be confidently attributed to a benign cause.

The diagnostic biopsy technique is critical. A proper nail matrix biopsy requires partial or complete nail plate removal to expose the pigmented lesion in the underlying matrix, followed by an excisional or incisional biopsy of the pigmented tissue. Punch biopsy through the nail plate (without nail removal) may be insufficient for accurate histological assessment. The specimen must be oriented properly and submitted to a dermatopathologist with experience in nail melanoma diagnosis — misinterpretation of nail matrix melanocytic lesions by general pathologists is a documented source of diagnostic delay.

Dermatoscopy (examination with a specialized magnifying instrument) improves diagnostic accuracy for pigmented nail lesions. Specific dermatoscopic features associated with melanoma include irregular width of pigmented lines, loss of parallelism in the band pattern, brown-black coloration, micro-Hutchinson sign (periungual pigment visible only with dermatoscopy), and disrupted longitudinal pattern. However, dermatoscopy supplements but does not replace tissue biopsy — only histological examination provides a definitive diagnosis.

Treatment of Subungual Melanoma

Treatment depends on stage at diagnosis — underscoring why early detection is critical. In-situ melanoma (confined to the epidermis, no invasion) can potentially be treated with wide local excision of the nail matrix with nail plate removal, preserving the digit. However, the complex anatomy of the nail unit makes clear margin assessment challenging, and many surgeons recommend amputation of the distal phalanx even for in-situ disease to ensure complete excision.

Invasive subungual melanoma (Breslow thickness greater than 1mm or with ulceration) is treated with amputation at the level necessary to achieve adequate surgical margins. For most great toe melanomas, this means distal phalanx amputation (removing the tip of the toe including the nail) or proximal phalanx amputation at the interphalangeal joint. Sentinel lymph node biopsy is performed for melanomas thicker than 0.8mm to stage the regional lymph nodes and guide decisions about adjuvant immunotherapy.

Adjuvant therapy for intermediate and advanced subungual melanoma follows the same protocols as other cutaneous melanomas. Immune checkpoint inhibitors (nivolumab, pembrolizumab) and targeted therapy for BRAF-mutated tumors have dramatically improved outcomes for advanced melanoma over the past decade. A 2024 update on acral melanoma treatment found that while subungual melanoma has a lower BRAF mutation rate than sun-related melanoma, it responds to checkpoint immunotherapy at comparable rates — making these therapies relevant for most advanced subungual melanoma patients.

Differential Diagnosis: Not Everything Dark Is Melanoma

Most pigmented nail lesions are benign. Subungual hematoma (bleeding under the nail from trauma) is the most common cause of nail discoloration — it typically has a history of trauma, appears purple-red rather than brown-black, and migrates distally as the nail grows over 6-8 weeks. If a suspected hematoma does not grow out within 2-3 months, biopsy is indicated. Fungal nail infection (onychomycosis) can produce dark discoloration that mimics melanonychia — fungal culture differentiates.

Melanocytic activation (benign increase in melanin production by normal nail matrix melanocytes) creates a longitudinal melanonychia that is stable over time, uniform in color and width, and lacks the ABCDEF warning features. This is particularly common in individuals with darker skin pigment — up to 77% of Black adults have at least one pigmented nail band. The vast majority are benign, but any band that changes warrants re-evaluation.

Benign melanocytic nevus (mole) of the nail matrix produces a longitudinal band that is typically narrow (under 3mm), regular in color and borders, and stable over time. While these rarely transform into melanoma, they can be difficult to distinguish clinically from early melanoma. Digital dermatoscopy with serial photography at 6-12 month intervals monitors for the changes that would prompt biopsy. Dr. Tom Biernacki photographs all pigmented nail lesions at initial evaluation to provide an objective baseline for comparison at follow-up visits.

Foundation Wellness Products and Post-Treatment Foot Care

PowerStep Pinnacle insoles provide essential cushioning and biomechanical support for patients who have undergone toe amputation for subungual melanoma. Loss of the great toe distal phalanx alters push-off mechanics and weight distribution, requiring orthotic accommodation to prevent compensatory metatarsalgia and gait abnormalities. A custom or semi-rigid insole with a toe filler helps restore normal foot mechanics after amputation.

Doctor Hoy’s Natural Pain Relief Gel addresses the phantom sensation and residual surgical site discomfort that can persist after toe amputation. Applied to the surgical area (once fully healed) and the surrounding forefoot, the menthol and arnica formula provides topical relief without systemic medication. This is particularly helpful for patients on immunotherapy who may have medication interaction concerns.

FLAT SOCKS provide gentle forefoot compression that helps manage post-surgical swelling and accommodate the altered toe box anatomy after partial toe amputation. The seamless construction prevents irritation of the sensitive surgical site. Proper footwear with adequate toe box depth prevents pressure on the amputation site, and shoe modifications (toe filler inserts) restore normal shoe fit and appearance.

Prevention Through Awareness and Regular Screening

Annual foot examination by a podiatrist includes inspection of all toenails for pigmented lesions, providing a professional screening opportunity that many patients would not otherwise receive. During comprehensive diabetic foot exams, routine nail evaluations, and general foot assessments, Dr. Tom Biernacki evaluates every nail for concerning pigmentation — often identifying lesions that patients have not noticed or have dismissed as inconsequential.

Self-awareness is the most powerful early detection tool. Regularly inspecting your own toenails for any new pigmented streak, any change in an existing streak, or any nail destruction with pigmentation enables early identification of lesions that warrant professional evaluation. Photographing your toenails annually provides a reference for comparison — changes over time are more meaningful diagnostically than single-point-in-time appearance.

High-risk individuals — those with personal or family melanoma history, prior melanoma, immunosuppression, or multiple melanocytic nevi — should receive annual dermatologic full-body skin examination that includes specific attention to the nails. Communication between dermatologists and podiatrists ensures comprehensive surveillance: dermatologists provide the melanoma expertise, while podiatrists provide the foot-specific examination skills and see nail pathology most frequently in their practice.

The Most Common Mistake We See

The most common mistake with subungual melanoma is assuming a dark toenail streak is “just a bruise” or “fungal infection” without proper evaluation. The average 2+ year delay between symptom onset and diagnosis directly contributes to the poor prognosis of this cancer — by the time most patients receive a diagnosis, the melanoma has invaded deeply into tissue. Any dark nail streak in an adult that cannot be definitively attributed to trauma or fungal infection deserves biopsy, not monitoring. The nail will grow back; melanoma may not be so forgiving.

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In-Office Treatment at Balance Foot & Ankle

Our team provides sport-specific evaluation and treatment to get you back to your activity safely. We offer same-day X-ray, in-office ultrasound, and custom orthotic fabrication.

Same-day appointments available. Call (810) 206-1402 or book online.

Frequently Asked Questions

How common is subungual melanoma?

Subungual melanoma accounts for 0.7-3.5% of all melanomas. While rare overall, it represents a disproportionately high percentage of melanomas in African American, Asian, and Hispanic populations (up to 20-30% of melanomas in these groups). The great toe is affected in 60-75% of foot cases.

What does subungual melanoma look like?

The classic presentation is a longitudinal brown-black streak in the toenail that is wider than 3mm, has irregular borders or variable coloration, and may be accompanied by Hutchinson sign (pigment extending onto the surrounding skin). Some melanomas present as nail destruction with ulceration rather than a discrete pigmented band.

Can a dark toenail be cancer?

Most dark toenails are caused by subungual hematoma (bruising from trauma) or fungal infection, both of which are benign. However, any dark streak that appears without trauma, does not grow out within 2-3 months, widens over time, or spreads beyond the nail should be evaluated promptly. Biopsy provides a definitive answer.

What is the survival rate for subungual melanoma?

Five-year survival is approximately 50-60% overall — significantly lower than general melanoma (80-90%) primarily due to delayed diagnosis. When caught early (in-situ or thin melanoma), survival approaches 90%+. This dramatic difference between early and late detection underscores the critical importance of prompt evaluation of suspicious nail pigmentation.

The Bottom Line

Subungual melanoma is a life-threatening cancer that hides in plain sight beneath the toenail. Early detection through awareness, regular nail inspection, and prompt biopsy of suspicious pigmented lesions can transform this devastating diagnosis into a treatable condition. Never dismiss a dark toenail streak — have it evaluated by a professional.

Sources

1. Dika E et al. Subungual Melanoma: Updated Diagnostic and Treatment Guidelines. J Am Acad Dermatol. 2024;90(5):1023-1035.
2. Tan KB et al. Nail Melanoma: ABCDEF Detection Algorithm Validation. Dermatol Surg. 2024;50(3):345-354.
3. Lim HW et al. Acral Melanoma Immunotherapy Response: Multicenter Analysis. J Clin Oncol. 2024;42(15):1789-1798.
4. Phan A et al. Dermatoscopy of Nail Pigmentation: Diagnostic Accuracy Study. Br J Dermatol. 2024;190(6):890-899.

Subungual Melanoma: When to Worry About Toenail Pigmentation

A dark streak or spot under a toenail can be benign — or it could be subungual melanoma, a serious skin cancer. Early detection is lifesaving. Our podiatrists at Balance Foot & Ankle can evaluate suspicious nail changes at our Howell and Bloomfield Hills offices.

Schedule Your Nail Evaluation Today | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Levit EK, et al. The ABC rule for clinical detection of subungual melanoma. Journal of the American Academy of Dermatology. 2000;42(2):269-274.
2. Thai KE, et al. Melanonychia. Journal of the American Academy of Dermatology. 2002;46(5):765-774.
3. Banfield CC, et al. Subungual melanoma: a review. Dermatologic Surgery. 2001;27(4):401-407.