If melanoma is diagnosed, the doctor needs to know the stage
, or extent, of the disease to plan the best treatment. Staging is a careful attempt to find out whether the cancer has spread, and if so, to what parts of the body.
The Spreading of Cancer
There are three ways that cancer spreads in the body:
Cancer invades the surrounding normal tissue.
Through the lymph system.
Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
Through the blood.
Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary tumor and travel through the lymph or blood to other places in the body, another, or secondary tumor, may form. This process is called metastasis
. The secondary, or metastatic, tumor is the same type of cancer as the primary tumor. For example, if melanoma spreads to the bones, the cancer cells in the bones are actually melanoma cancer cells. The disease is metastatic melanoma, not bone cancer.
Stages of Melanoma
In stage 0, the melanoma cells are found only in the outer layer of skin cells and have not invaded deeper tissues.
Melanoma in stage I is thin, the tumor is no more than 1 millimeter (1/25 inch) thick. The outer layer (epidermis) of skin may appear scraped. (This is called an ulceration
). Or, the tumor is between 1 and 2 millimeters (1/12 inch) thick. There is no ulceration. The melanoma cells have not spread to nearby lymph nodes.
The tumor is at least 1 millimeter thick. There is ulceration. Or, the thickness of the tumor is more than 2 millimeters. There may be ulceration. The melanoma cells have not spread to nearby lymph nodes.
The melanoma cells have spread to nearby tissues: The melanoma cells have spread to one or more nearby lymph nodes. Or, the melanoma cells have spread to tissues just outside the original tumor but not to any lymph nodes.
The melanoma cells have spread to other organs, to lymph nodes, or to skin areas far away from the original tumor.