If you are diagnosed with melanoma—a rare but serious type of skin cancer—your doctor will also need to determine the stage of melanoma. The exact stage of melanoma will be important in choosing the appropriate treatment for the skin cancer.
Stages of melanoma, like with other types of cancer, refer to how the cancer is progressing and spreading (or “metastasizing”) throughout the body. The higher the stage, the more serious the melanoma is and the harder it is to treat and prevent melanoma recurrence.
Factors That Determine Staging
“When we look at the staging of melanoma, we’re interested in three things: TNM, [or] tumor, node, metastasis,” says Kaveh Alizadeh, MD, plastic and reconstructive surgeon in New York City. “Depending on a combination of these, you can end up in different stages.”
Doctors will look at the thickness and appearance of the tumor. If the tumor is only affecting the dermis or epidermis (the top two layers of the skin), these will be a lower stage of melanoma. Tumors are categorized by a “T stage,” using the following scale:
T1 is less than or equal to 1.0 mm.
T2 is between 1.0 and 2.0 mm.
T3 is between 2.1 and 4.0 mm.
T4 is greater than 4.0 mm.
Nodes, meaning the lymph nodes, are the first thing to be affected whenever a cancer spreads. Lymph nodes are located throughout the body and are part of the immune system.
First, this may be “micro-metastasis,” which is when “the node itself doesn’t look enlarged but there’s tiny infiltration of [cancer] cells into that node,” says Dr. Alizadeh. When lymph nodes are fully affected, they become swollen and help spread melanoma throughout the body.
Doctors categorize nodal involvement with the “N stage,” using the following scale:
N0 means no nodes are affected by melanoma.
N1 means one nearby node is affected.
N2 means two or three nodes are affected.
N3 means more than four nodes are affected.
Metastasis can also occur at different degrees of severity. Doctors will determine if the metastasis or regional (affecting only nearby lymph nodes and organs) or distant (reaching nodes and organs that are far from the tumor). Metastasis is categorized by the “M stage,” using the following scale:
M0 means no metastasis has occurred.
M1a means metastasis to skin layers or distant lymph nodes.
M1b means metastasis to lung.
M1c means any other distant form of metastasis.
Because higher stages come with a higher risk of melanoma recurrence, catching melanoma early can truly be life-saving. Those who are treated in the early stages tend to have a better chance of survival and enjoy a longer life. For example, the 10-year survival rate for someone treated in stage 1 melanoma is more than 90 percent, according to the American Cancer Society.
“The good news for people that have later stage melanomas is that they have more potential for disease-free survival, and more potential with some of these newer treatments that are out there to fight the tumors for them,” says Dr. Alizadeh.