Melanoma is a cancerous growth of melanocytes that produce melanin. The type of melanoma that typically affects the toenail is acral lentiginous melanoma. In the United States, acral lentiginous melanoma (ALM) accounts for about 5% of all diagnosed melanomas. It also is the most common form of melanoma in Asians and people with dark skin, accounting for 50% of melanomas that occur in people with these skin types.
ALM is sometimes referred to as a “hidden melanoma” because these lesions occur on parts of the body not easily examined or not thought necessary to examine. ALM develops on the palms, soles, mucous membranes (such as those that line the mouth, nose, and female genitals), and underneath or near fingernails and toenails.
ALM is often overlooked until it is well advanced because in the early stages, it often looks like a bruise or nail streak. Here is what it usually looks like on each area of the body:
• Palm or sole – Melanoma usually begins as an irregularly shaped tan, brown, or black spot. It is often mistakenly attributed to some recent injury — that is, the patient recalls a relatively recent bruise or blow in the general area of the pigmented spot.
• Mucous membranes – When melanoma develops on a mucus membrane, it is most likely to develop inside the nose or mouth. Early symptoms include nosebleeds and nasal stuffiness and a pigmented mass inside the mouth. Melanomas also can develop on the mucous membranes of the anus, urinary tract, and female genitalia.