When you are diagnosed with melanoma, your doctor will tell you what stage melanoma you have. “Stage” is a way to describe the severity of a cancer by incorporating information about its location, size, whether it has spread to nearby lymph nodes, and whether it has metastasized to other parts of the body. In the case of melanoma, stages I and II are based mainly on the thickness of the cancer and how many layers of skin it has invaded. Stages III and IV are based on how far the melanoma has spread from the skin. Staging is based on a combination of physical examination, biopsy, and investigation of the lymph nodes and other parts of the body.
After melanoma has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.
Melanoma cancers are staged as follows:
Melanoma in situ, or stage 0
Does not reach below the surface of the skin.
Stage IA melanoma is less than 1 millimeter thick and has not ulcerated. It is most likely present only in the top layer of the skin.
Stage IB melanoma also may be less than 1 millimeter thick but has ulcerated (become an open sore) and may have grown into deeper layers of the skin.
Stage IIA melanoma is either 1 to 2 millimeters thick with ulceration or 2 to 4 millimeters thick with no ulceration.
Stage IIB melanoma is either 2 to 4 millimeters thick with ulceration or more than 4 millimeters thick without ulceration.
Stage IIC melanoma is more than 4 millimeters thick with ulceration.
Stage III melanoma has spread to the lymph system or directly into the lymph nodes near the cancer, and may also have spread directly from the original tumor to areas more than 2 centimeters away (but not to farther lymph nodes).
Stage IV melanoma has metastasized to more distant lymph nodes and/or to other organs.