Foot Melanoma: Recognition, Biopsy, and What Diagnosis Means for Treatment

Melanoma of the foot is a medical emergency masquerading as a benign skin change. Acral lentiginous melanoma (ALM) — the subtype that occurs on the soles, palms, and nail units — is the most common melanoma subtype in people of color, but it affects all ethnicities with equal frequency regardless of sun exposure history. The tragedy of foot melanoma is almost always the same: delayed diagnosis because no one thought to look.

What Makes Foot Melanoma Different

Acral lentiginous melanoma differs from the more common superficial spreading melanoma in three clinically important ways. First, it has no relationship to ultraviolet radiation exposure — it cannot be prevented by sunscreen or avoided by minimizing sun exposure, making it an equal-opportunity cancer. Second, it disproportionately affects darker skin phototypes (Fitzpatrick types V–VI) while standard melanoma prevention messaging focuses on light-skinned individuals — creating a deadly awareness gap. Third, and most critically, it occurs in areas that receive essentially no routine skin examination: the plantar surface, between the toes, and under the nails. These three factors combine to produce a cancer that is almost always diagnosed late, explaining its worse overall prognosis compared to other melanoma subtypes.

Plantar Melanoma: Stages and Prognosis

Stage (AJCC 8th)	Description	5-Year Survival	Breslow Depth	Treatment Overview
Stage IA	Thin, localized; no ulceration; no lymph node spread	~97%	<0.8mm without ulceration	Wide local excision (1cm margins); no SLNB required
Stage IB	Thin with ulceration OR 0.8–1.0mm	~92%	0.8–1.0mm; OR any <0.8mm with ulceration	Wide excision; consider SLNB
Stage IIA–IIB	Intermediate thickness; possible ulceration	~65–80%	1.0–4.0mm ± ulceration	Wide excision (2cm margins); SLNB; possible adjuvant therapy
Stage IIC	Thick with ulceration; no nodal spread	~53%	>4mm with ulceration	Wide excision; SLNB; adjuvant immunotherapy
Stage III	Regional lymph node spread OR in-transit metastasis	~40–70% (varies by substage)	Any	Wide excision + therapeutic lymph node dissection; adjuvant pembrolizumab or nivolumab
Stage IV	Distant metastasis (visceral, distant LN, skin)	~15–20%	Any	Systemic therapy (immunotherapy: pembrolizumab, nivolumab, ipilimumab; targeted: BRAF inhibitors if BRAF-mutant)

Warning Signs Specific to Foot Melanoma

On the plantar surface: an irregular brown or black pigmented area that does not wipe away, does not fit neatly within the skin lines (dermatoglyphics), has uneven borders, or contains multiple shades of brown, black, gray, red, or white. Amelanotic (non-pigmented) plantar melanoma — present in 5–15% of cases — appears as a pink, flesh-colored, or red irregular lesion and is easily mistaken for a wart, granuloma, or chronic wound. Under the nail: a dark streak (longitudinal melanonychia) that widens over time or extends onto the surrounding nail fold skin (Hutchinson’s sign). Any of these findings requires urgent biopsy — not watchful waiting, not “trying antibiotics,” not assuming it is a fungal nail.

The Biopsy Decision

Biopsy is the only way to diagnose melanoma definitively. For plantar lesions, excisional biopsy (removing the entire lesion with a narrow 1–2mm margin) is preferred when the lesion is small enough to allow it — this provides the complete specimen needed for pathological staging. Punch biopsy is used for larger lesions or those in functionally challenging locations. Shave biopsy should be avoided for suspicious pigmented lesions because it may transect the lesion and prevent accurate Breslow depth measurement. After biopsy, if melanoma is confirmed, re-excision to appropriate margins is performed based on Breslow depth. On the plantar surface, wide excision often requires skin grafting due to the limited mobility of plantar skin.

Balance Foot & Ankle evaluates all suspicious foot and nail lesions with dermoscopy and performs biopsy when indicated. We refer confirmed melanoma cases to dermatology and oncology for surgical and systemic treatment coordination. If you have a suspicious lesion on your foot or nail that has not been evaluated, call (810) 206-1402 today. Early detection of foot melanoma is curative.