Malignant melanoma is a type of skin cancer that arises in melanocytes, the cells that produce melanin, or skin pigment. Melanoma is less common than other types of skin cancers, but it is more likely to spread to other areas of the body, according to the American Cancer Society. Like other cancers, melanoma is staged according to the spread and extent of the cancer; this staging helps guide treatment and prognosis.
Stage 0 (Melanoma in Situ)
In Stage 0 melanoma, abnormal melanocytes are seen in the epidermis, the outermost layer of skin, according to the National Cancer Institute. While these abnormal cells are not cancer, they may become cancerous and invade tissues that are surrounding them.
Stage I
There are two stages in this first stage of melanoma. Stage IA consists of a lesion that is less than 1 mm thick and has no skin breaks or ulcerations. The lesion is in the epidermis and the inner layer of skin known as the papillary dermis. Stage IB defines a lesion that is less than 1 mm thick with breaks in the skin, or it has spread from the dermis to the subcutaneous layer, below the skin. It can also reference a lesion that is between 1 and 2 mm thick, with no ulceration, according to the National Cancer Institute.
Stage II
This stage has three substages: Stage IIA, IIB, and IIC. Stage IIA encompasses a tumor that is either between 1 and 2 mm thick with breaks in the skin, or 2 to 4 mm with no breaks. Stage IIB describes a lesion that is 2 to 4 mm thick, with ulceration, or more than 4 mm thick with no ulceration. The last substage, Stage IIC, consists of lesions that are more than 4 mm thick and are ulcerated.
Stage III
According to the American Cancer Society and National Cancer Institute, this stage has three substages as well, similar to Stage II. Stage III melanoma cancers can be any thickness, it may or may not be ulcerated, and it has spread to one to three lymph nodes. The exception to this is Stage IIIC, which may be diagnosed if the cancer is in four or more lymph nodes, with no distant spread. The substages depend on whether the nodes are enlarged and whether the cancer has spread to nearby skin or tissue.
Stage IV
In this stage of malignant melanoma, the lesion can be any size, and cancer has been found in distant organs such as the liver or brain, or distant areas of the skin, according to the American Cancer Society. It does not matter how many lymph nodes are affected or how thick the lesion is.
