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Understanding Your Stage of Melanoma

The biopsy and other tests will help your doctor determine the thickness of your tumor. They will also help your doctor learn the extent of melanoma, called its stage. Melanoma may be located in one specific area of the skin, but it can move quickly to the lymph nodes. Your treatment plan and chance for a good outcome--called the prognosis--depend on the stage of your melanoma. They also depend upon your general health, the location of the tumor, and other factors.

The TNM System

Doctors use different systems to measure the thickness of a melanoma and to stage the disease. These systems summarize the extent of your cancer. The American Joint Committee on Cancer (AJCC) staging system is used most often for melanoma. It is called the TNM system.

  • The T stands for tumor. This category is based on the melanoma's thickness and whether or not it is ulcerated. The term ulcerated means that the layer of skin covering the melanoma is gone. There may be bleeding with ulceration.

  • N stands for lymph nodes. Lymph nodes are small groups of cells that help the body fight infections. This category indicates whether or not the melanoma has spread to the lymph nodes.

  • M stands for metastasis. This category tells whether or not the cancer has spread to distant organs.

The TNM system measures the thickness of the melanoma. The Breslow measurement uses a ruler-like device to measure the actual thickness of the melanoma in millimeters under a microscope. The Clark measurement describes the thickness of the melanoma in relation to how far it penetrates into the layers of the skin. In general, thinner or lower stage melanomas have a better prognosis.

Understanding the Numbers Used in Staging

Stages are named using a combination of 0 or the Roman numerals I to IV. The letters A through C are for substages. Lower stage cancers have a better outlook.

Stage 0. The melanoma is only in the top layer of skin, called the epidermis. This is also called melanoma in situ. In situ means the cancer has remained confined, and has not invaded other tissues.

Stage IA. The tumor is in the epidermis and the upper part of the layer of skin under the epidermis, called the dermis. It is no more than 1 millimeter thick, with no ulceration, and appears to be growing slowly (has a low mitotic rate).

Stage IB. The tumor is 1 to 2 mm thick, with no ulceration. Or, it is not more than 1 mm thick, with ulceration, or a high mitotic rate.

Stage IIA. The tumor is 1 to 2 mm thick with ulceration. Or, it is 2 to 4 mm thick with no ulceration.

Stage IIB. The tumor is between 2 and 4 mm thick, with ulceration. Or, it is more than 4 mm thick with no ulceration.

Stage IIC. The tumor is thicker than 4 mm and is ulcerated.

Stage III. The tumor may be any thickness. In addition, one of these is also true:

  • Stage IIIA is when surgical removal of the lymph node confirms that the tumor has spread into one to three nearby lymph nodes, but the nodes are not enlarged and the melanoma is only found when they are looked at under a microscope. The melanoma is not ulcerated.

  • Stage IIIB means the tumor has spread to the lymphatic channels or to one to three lymph nodes, which may or may not be enlarged. The melanoma may or may not be ulcerated.

  • Stage IIIC means the melanoma is ulcerated and has spread either to the lymphatic channels or to one to three nearby lymph nodes which are enlarged. Or,the cancer has spread to 4 or more lymph nodes, to lymph nodes that are clumped together, or to both nearby lymph nodes and lymphatic channels. 

  • Stage IV. The tumor may be any thickness, with or without ulceration. It has spread to distant lymph nodes, areas of skin, or other organs in the body.