melanoma (MEH-luh-NOH-muh) A form of skin cancer that begins in melanocytes (the cells that make the pigment melanin). Melanoma usually begins in a mole.

melanin (MEL-a-nin) The substance that gives color to skin and eyes.

melanocyte (mel-AN-o-site) A cell in the skin and eyes that produces and contains the pigment called melanin.

melanoma vaccine A cancer vaccine prepared from human melanoma cancer cells. It can be used alone or with other therapy in treating melanoma.

stage 0 melanoma Cancer is found in the epidermis (outer layer of the skin) only. Also called melanoma in situ.

stage I melanoma Stage I is divided into stages IA and IB. In stage IA, the tumor is not more than 1 millimeter thick, with no ulceration. The tumor is in the epidermis (outer layer of skin) and upper layer of the dermis (inner layer of skin). In stage IB, the tumor is either not more than 1 millimeter thick, with ulceration, and may have spread into the dermis or the tissue below the skin; or 1 to 2 millimeters thick, with no ulceration.

stage II melanoma Stage II is divided into stages IIA, IIB, and IIC. In stage IIA, the tumor is either 1 to 2 millimeters thick, with ulceration; or 2 to 4 millimeters thick, with no ulceration. In stage IIB, the tumor is either 2 to 4 millimeters thick, with ulceration; or more than 4 millimeters thick, with no ulceration. In stage IIC, the tumor is more than 4 millimeters thick, with ulceration.

stage IIB melanoma Melanoma in which the tumor is more than 4 millimeters thick. It has spread through the lower part of the inner layer of skin (dermis) and into subcutaneous (under the skin) tissue, but not to nearby lymph nodes.

stage III melanoma The tumor may be any thickness, with or without ulceration (formation of a break on the skin or surface of an organ), and (1) has spread to 1 or more lymph nodes; or (2) has spread into the nearby lymph system but not into nearby lymph nodes; or (3) has spread to lymph nodes that are matted (not moveable); or (4) satellite tumors (additional tumor growths within 2 centimeters of the original tumor) are present and nearby lymph nodes are involved.

stage IV melanoma The tumor may be any thickness, with or without ulceration (formation of a break on the skin or surface of an organ), may have spread to 1 or more nearby lymph nodes, and has spread to other places in the body.