Melanoma is a form of skin cancer that can be very dangerous if left untreated. It develops within the skin, and affects various layers of the skin depending on the stage of the cancer. The prognosis for melanoma depends on the depth of invasion of the cancer cells within the three layers of the skin: the epidermis (the outermost layer), the dermis (the thick layer below the epidermis) and the adipose tissue (the layer of fat below the skin).
Staging
Cancer prognoses depend in large part on how far the cancer has developed. The American Joint Committee on Cancer (AJCC) has developed a system of stages for classifying the progress of the cancer called the TNM system. The letters TNM refer to the three factors used in staging cancer: the size of the tumor ("T"), the lymph node involvement ("N") and the metastasizes or spreads of the cancer to other parts of the body ("M"). Melanoma has 5 stages, between 0 and IV, with Stage 0 cancer having nearly a 100 percent survival rate while the five-year survival rate for Stage IV comes in as low as 14 percent.
Stage IIIA
Stage IIIA melanomas have a T number between 1a and 4a, an N number of 1a or 2a and an M number of 0. This means that 3 lymph nodes local to the infected skin area are involved. However, the lymph nodes have not enlarged despite the presence of cancer cells, and the melanoma is apparent in the lymph nodes only with the use of a microscope. The tumor can measure between 1 to 4 mm but is not ulcerated, and there is no metastasis (the cancer has not spread to other parts of the body).
Stage IIIB
There are three distinct sets of TNM numbers associated with Stage IIIB Melanoma. The first is a T number between 1b and 4b, meaning the tumor is between 1 and 4 mm long and is ulcerated. Like Stage IIIA, there is involvement in between 1 and 3 lymph nodes, but the melanoma is only seen under a microscope. Again, there is no metastasis.
The second set of numbers has a T number between 1a and 4a, an N number of 1b or 2b and an M number of 0. Under these circumstances, the melanoma is not ulcerated. The lymph node involvement is such that the affected 1-3 lymph nodes are enlarged. There is no metastasis.
The final TNM numbers include a T number between 1 and 4 (a or b), an N number of 2c and an M number of 0. This means it does not matter whether the tumor is ulcerated or not, the tumor can measure between 1 and 4 mm, and there is no metastasis. These numbers are characterized by the fact that the cancer has spread to nearby skin or lymph nodes, but the lymph nodes themselves do not contain melanoma.
Stage IIIC
Stage IIIc has two distinct sets of TNM numbers that are associated with it. The first is a T number between 1 and 4b, an N number of 1 or 2b and an M number of 0. The tumor is thus between 1 and 4 mm, and ulcerated. There is lymph node involvement with lymph nodes that are enlarged by the melanoma. There is no metastasis.
The second factors that indicate a diagnosis of Stage IIIc are any T number, an M number of 0 and an N number of 3. There is no metastasis, and the tumor can be any size and ulcerated or not. The N number of 3 is the key factor here, and it means that 4 lymph nodes, or a clump of lymph nodes, have melanomas, or the skin and lymphatic channels around the tumor show melanoma. The lymph nodes are enlarged as a result of the cancer cells.
Prognosis
At the time of the American Cancer Society's most recent study, Stage IIIA was a new stage so there were no five-year survival rates. Thus statistics are not available for this group.
The five-year survival rates for those with Stage IIIB are between 50 and 68 percent. Survival rates over 10 years are between 44 and 60 percent.
Stage IIIC five-year survival rates are between 27 and 52 percent. After 10 years the figures fall between 22 and 37 percent.
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