⚠ Critical Warning — When to Act Immediately: A dark streak (brown or black) under a toenail that you don’t remember injuring, or a dark spot on the sole of your foot that is growing, changing color, or has irregular borders, requires urgent podiatric evaluation. Subungual melanoma — melanoma under the nail — is rare but deadly when missed. In our Howell and Bloomfield Hills clinics, we evaluate suspicious nail and foot skin lesions regularly. When in doubt, have it checked immediately. Call (810) 206-1402 for a prompt evaluation.

Can You Get Cancer in Your Foot or Toenail?

Yes — though rare, several types of cancer can affect the foot, toes, and toenails. The most clinically significant is subungual melanoma, a form of melanoma that develops beneath the nail plate. Because it’s often mistaken for a bruise, fungal infection, or trauma-related discoloration, it is frequently diagnosed at a late stage — dramatically worsening outcomes.

What Dr. Tom Tells His Patients: “The most dangerous thing about subungual melanoma is that it looks harmless. I’ve had patients tell me they thought the dark stripe under their toenail was from wearing tight shoes or an old injury. If there’s no clear trauma history and the streak isn’t growing out with the nail, that needs to be evaluated. I’d rather biopsy ten benign lesions than miss one melanoma.”

Subungual Melanoma: The Most Dangerous Toenail Cancer

Subungual melanoma originates from melanocytes (pigment-producing cells) in the nail matrix — the tissue under the base of the nail. It most commonly presents as a longitudinal melanonychia: a dark brown or black stripe running the length of the nail. It accounts for roughly 0.7–3.5% of all melanomas in white populations but up to 20–35% of melanomas in people with darker skin tones, making racial awareness critical for both patients and clinicians.

ABCDEs of Subungual Melanoma

• A — Age/African American: Most common in patients over 50; higher prevalence in darker-skinned populations
• B — Brown or Black band: Width greater than 3mm, multiple colors, or blurred borders
• C — Change: Rapid change in size, shape, or color of the pigmented band
• D — Digit involved: Thumb and great toe are highest risk — a single digit lesion in an adult is more suspicious than multiple lighter bands
• E — Extension of pigment: Hutchinson’s sign — pigment extending from the nail onto the surrounding skin (proximal or lateral nail fold). This is a serious warning sign.

A 2024 review in the Journal of the American Academy of Dermatology found that 5-year survival for subungual melanoma is 87% when caught at Stage I but drops to 20% at Stage IV — underscoring the critical importance of early evaluation. (JAAD, 2024)

Other Cancers Affecting the Foot and Toes

Squamous Cell Carcinoma (SCC)

SCC is the most common malignant skin cancer of the foot. It typically presents as a chronic, non-healing ulcer or firm plaque on the plantar foot or around the nail. It can be mistaken for a plantar wart, chronic wound, or fungal infection. Risk factors include chronic sun exposure (dorsum of foot), HPV infection (particularly HPV types 16 and 18 in periungual lesions), chronic ulcers, and prior radiation.

Basal Cell Carcinoma (BCC)

BCC on the foot is rare (the foot receives less cumulative UV than the face or arms) but does occur, most commonly on the dorsal foot. It typically appears as a pearlescent or translucent nodule with telangiectasias (visible blood vessels). It rarely metastasizes but requires complete excision.

Soft Tissue Sarcomas

Soft tissue sarcomas (synovial sarcoma, clear cell sarcoma, epithelioid sarcoma) can arise in the foot and ankle. They often present as a slowly growing, painless mass — which is exactly why they are frequently ignored or misdiagnosed as a benign cyst or ganglion. Any firm, fixed, or growing mass in the foot or ankle warrants imaging (MRI) and possible biopsy regardless of pain level.

Kaposi Sarcoma

Kaposi sarcoma commonly affects the lower extremities, including the feet, in immunocompromised patients (HIV/AIDS, transplant recipients). It presents as violaceous (purple-red) patches, plaques, or nodules. Podiatrists are often the first clinicians to identify lower extremity Kaposi sarcoma lesions.

What Is NOT Cancer: Common Mimics

Most dark toenail or foot lesions are benign. Common mimics that are NOT cancer:

• Subungual hematoma — blood under the nail from trauma. Grows out with the nail; no color extension onto the nail fold
• Nail fungus (onychomycosis) — white, yellow, or brown discoloration with thickening; rarely dark black; responds to antifungal treatment
• Ethnic melanonychia — normal dark longitudinal bands in people with darker skin tones; multiple nails often affected; no change over time
• Plantar warts (verruca plantaris) — HPV-caused lesions that can resemble SCC; lack a skin line pattern interrupted by a central core
• Benign blue nevus or dermatofibroma — stable, well-demarcated skin lesions

The key distinction is change: a stable, unchanging lesion with a clear benign history is much less concerning than a growing, changing, or symptomatic lesion. When in doubt, biopsy resolves the question definitively.

Diagnosis: What to Expect at Your Appointment

• Clinical examination — dermoscopy (dermatoscope magnification) to visualize nail and skin pigment patterns
• Nail biopsy — the definitive test for suspicious nail lesions; performed under local anesthesia in-office; the nail plate is partially removed to access the nail matrix
• Skin punch biopsy — for suspicious cutaneous lesions on the dorsal or plantar foot
• MRI or ultrasound — for soft tissue masses suspected of being sarcomas
• Sentinel lymph node biopsy — if melanoma is confirmed, to assess for lymph node spread (coordinated with dermatology/oncology)

When to Seek Immediate Evaluation

• Any dark (brown or black) streak under a toenail appearing without clear trauma history
• Pigment extending from the nail onto the surrounding skin (Hutchinson’s sign)
• A toenail lesion that does not grow out with the nail over 2–3 months
• Any non-healing wound, ulcer, or growth on the foot present for more than 6 weeks
• A firm, growing mass anywhere on the foot or ankle — even if painless
• Any skin lesion on the foot that is asymmetric, has irregular borders, multiple colors, or is larger than 6mm

At Balance Foot & Ankle Specialists, Dr. Tom Biernacki performs in-office nail biopsies and can coordinate urgent dermatology and oncology referrals for confirmed or suspected malignancy. Do not wait months for a routine appointment if you have a concerning lesion. Call (810) 206-1402 or visit our New Patient Information page. We serve patients in Howell, MI and Bloomfield Hills, MI.

Medical References & Sources

• American Podiatric Medical Association — Patient Education
• American Orthopaedic Foot & Ankle Society — Foot Conditions