Melanoma is a type of skin cancer that can rarely develop beneath the surface of the nail. Called subungual (under the nail) melanoma, it appears as a brown or black streak. People may delay seeing a doctor because they mistake the discoloration for a bruise, assuming they’ve stubbed their toe or hit a finger.
Subungual melanoma often occurs in non-Caucasians. Only about 2% of cases are in white-skinned individuals whereas about 30-40% of cases are in non-whites. Subungual melanoma accounts for 75% of melanomas in Blacks. However, many dark-skinned people may have streaks in their nails that are not cancer; these do not change or increase in size and usually affect multiple nails. Men and women are at equal risk, and the risk increases after age 50.
Most subungual melanomas occur in the thumbnail or big toenail, although it can develop in any nail. Repeated injury to finger- or toenails has been identified as a risk factor for developing subungual melanoma.
Like other forms of melanoma that typically surface on skin, subungual melanoma can spread to other parts of the body, including organs and lymph nodes — and it can be deadly. Always see a dermatologist as soon as possible if you notice potential signs of subungual melanoma.
The following can be signs of a nail (subungual) melanoma:
- A brown or black streak in the nail (most commonly the great toe and thumb)
- Streaks that increase in size over time
- No known injury to the nail
- A bruise that does not heal or grow out with the nail
- Nail separating from nail bed
- An ulcer, nodule or bleeding developing in or around the nail
- Darkening skin on the cuticle or skin next to nail (advanced stage)
- Deformed and damaged nail (advanced stage)
The outlook for this type of melanoma is poorer than for others because diagnosis is often delayed. There is a lack of awareness of the risk of skin cancer in skin of colour. The five-year survival rate for subungual melanoma can vary greatly – from 16 to 87%– depending how extensively the cancer has spread.
Treatment involves surgically removing the melanoma, often involving the whole nail. Sometimes the end of the affected finger or toe is also amputated, but doctors try to avoid this. Sampling a lymph node is sometimes required to determine whether the melanoma has spread to the lymph nodes.