Size or thickness of the melanoma, whether or not it has spread to the lymph nodes or other organs, growth rate, ulceration determines the stage of melanoma.
The American Joint Commission on Cancer has developed the TNM staging system, composed of three key pieces of information:
- Tumor (T) describes features of the tumor, including how deep it grows into the skin (thickness, known as the Breslow measurement), rate of dividing (mitotic rate), and the presence or absence of ulceration.
- Node (N) describes whether or not melanoma has spread to nearby lymph nodes.
- Metastasis (M) describes whether the melanoma has spread to distant organs. The levels of LDH, a substance in the blood, is also a determination factor.
Clinical staging bases on information collected before surgery, including physical exam and imaging results. Pathologic staging combine the clinical information with pathological findings from the surgical or biopsy samples after the procedure, therefore is more accurate.
- Stage 0 melanoma means the cancer cells are confined to the top layer of the skin (epidermis).
- Stage I melanoma means the cancer cells have grown beyond epidermis, but have not spread to the lymph nodes or other parts of the body.
- Stage IA: The cancer is less than 1 mm deep, does not appear ulcerated, nor dividing rapidly.
- Stage IB: The cancer is either less than 1 mm deep but is ulcerated or dividing more rapidly, OR the cancer is between 1-2 mm deep without any sign of ulceration.
- Stage II melanoma means the cancer cells have grown deeper into the skin, or have more high-risk features, but have not spread to the lymph nodes or other parts of the body.
- Stage IIA: The cancer cells have grown 1-2 mm deep into the skin, and the tumor appears ulcerated, OR the cancer is 2-4 mm deep but is not ulcerated.
- Stage IIB: The cancer is 2-4 mm thick with ulceration, OR thicker than 4 mm but not ulcerated.
- Stage IIC: The cancer is more than 4 mm thick, and it is ulcerated.
- Stage III melanoma means the melanoma cancer cells have spread to nearby lymph nodes, but not to distant organs.
- Stage IV melanoma means the cancer cells have spread beyond the skin and regional lymph nodes to distant organs such as the liver, lungs or brain, or distant lymph nodes and areas of the skin.