The stage of a cancer is how much and how far the cancer has spread in your body. Your health care provider uses exams and tests to find out the size of the cancer and where it is. He or she can also see if the cancer has grown into nearby areas, and if it has spread to other parts of your body. The stage of a cancer is one of the most important things to know when deciding how to treat the cancer.
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 it is ulcerated. The thickness of the melanoma is called the Breslow measurement. 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 shows whether the melanoma has spread to nearby lymph nodes.
M stands for metastasis. This category tells whether the cancer has spread to distant organs.
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 (epidermis). This is also called melanoma in situ. In situ means the cancer has remained confined, and has not invaded deeper into the skin.
Stage IA. The tumor is in the epidermis and the upper part of the layer of skin under the epidermis (dermis). It is no more than 1 millimeter thick, with no ulceration. It 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 is ulcerated. It has spread to one to three nearby lymph nodes, but the node or nodes are not enlarged. The melanoma is only found when it is looked at under a microscope. Or the tumor is not ulcerated but the cancer has spread to one to three nearby lymph nodes. The node or nodes are enlarged. Or it has spread to nearby areas of skin or to the lymphatic channels.
Stage IIIC means the melanoma is ulcerated and has spread to nearby areas of skin, to the lymphatic channels, or to one to three nearby lymph nodes. The lymph node or nodes 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.