Melanoma is the most serious type of skin cancer and develops in cells (melanocytes) that make the pigment (melanin) for skin color. Melanoma is characterized by an irregularly-shaped skin growth that can be a variety of colors, such as white, pink, red, brown, black, or blue, can develop from an existing mole that becomes cancerous, or can appear as a separate skin growth.
There are three subtypes of melanoma: 1) acral lentiginous melanoma, 2) juvenile melanoma, and 3) malignant lentigo melanoma.
While melanoma more frequently appears on skin (cutaneous melanoma) that is occasionally exposed to the sun, this cancer can also appear in other areas of the body that have little or no exposure to the sun (acral lentiginious melanoma), such as the scalp, palms, genitals, toes, and soles of the feet (hidden melanoma). More rarely, melanoma can also form in the eyes (ocular melanoma) or inside the nose or throat.
While melanoma can appear at any age, it occurs more frequently in older people between the ages of 50 and 70 (malignant lentigo melanoma); however, the rates of melanoma have been increasing over the last thirty years, as well as appearing more frequently in young adults.
Juvenile melanoma can be either a cancerous or non-cancerous form of melanoma and usually occurs before puberty.
Melanoma tumors are more commonly found on the back in men and on the legs in women. While melanoma more commonly affects the outer layer of skin (epidermis), as the cancer grows, involving more layers of skin, it can also spread to other parts of the body (metastasize).
Melanoma is classified by the following stages:
Stage 0 (Melanoma in situ) – In this stage of melanoma, abnormal cells that produce melanin (melanocytes) are present in the outer layer of the skin (epidermis) and may become cancerous and spread (metastasize).
Stage I (IA & IB) – In this stage of melanoma, the tumor is no larger than 1 millimeter thick, with or without a break in the skin (IA), or the tumor is more than 1, but not more than 2, millimeters thick, without a break in the skin (IB).
Stage II (IIA, IIB, & IIC) – In this stage of melanoma, the tumor is no larger than 1, but not more than 2, millimeters thick, with a break in the skin, or the tumor is more than 2, but not more than 4, millimeters thick, without a break in the skin (IIA), or the tumor is more than 2, but not more than 4, millimeters thick, without a break in the skin (IIB), or the tumor is more than 4 millimeters thick, with a break in the skin (IIC).
Stage III (IIIA, IIIB, IIIC, & IIID) - In this stage of melanoma, the tumor is not larger than 1 millimeter thick, with a break in the skin, or not larger than 2 millimeters, without a break in the skin, and the cancer has spread to multiple lymph nodes, or it is unknown where the primary cancer began, or the cancer is found in 1 lymph node, and there is tumor spread (metastases) on or under the skin, or the tumor is no larger than 1 millimeter thick, with a break in the skin, or not larger than 2 millimeters thick, without a break in the skin, and one of the following has also been found: 1) the cancer has spread to 1-to-3 lymph nodes, or there are microscopic tumors or tumor spread (metastasis) on or under the skin, or the tumor is larger than 1, but not more than 2, millimeters thick, with a break in the skin, or larger than 2, but not more than 4, millimeters thick, without a break in the skin.
Stage IV – In this stage melanoma, the cancer has spread (metastasized) to other parts of the body, such as distant lymph nodes, soft tissue, muscle, the brain, spinal cord, lung, liver, gastrointestinal tract, and bone, and the cancer may have spread far from the primary tumor.
