Making a melanoma diagnosis means gathering as much information about your skin cancer as possible. One key step is determining the cancer’s stage, which is a measure of the amount and severity of cancer in the body. Staging helps your doctor understand how best to treat the cancer, and is used when discussing survival rates.

Following stage 0 (called melanoma in situ), the degrees of melanoma range from stage I through stage IV, with higher numbers indicating further spreading of the cancer throughout the body.

There are three factors commonly used to determine melanoma staging, and they’re represented by the TNM system. The first factor is the severity of the primary tumor (T), which includes how thick the tumor is and whether the skin covering it has broken. The second factor is whether the cancer has spread to nearby lymph nodes (N). The third factor is whether the cancer has spread, or metastasized (M), to lymph nodes farther away in the body or other organs.

Stage I Melanoma

The earliest stage of melanoma, stage 0, is limited to the outermost skin layer called the epidermis. This is a noninvasive stage, which is also called melanoma “in situ,” meaning “in its original place.”

With stage I melanoma, the tumor’s thickness is 1mm or less. This tumor may or may not have ulcerated, and it isn’t yet believed to have spread beyond the original site.

Treatments for Stage I Melanoma

Your doctor will most likely treat stage 1 melanoma with surgery called wide excision, which cuts out the melanoma along with a margin of healthy surrounding skin. The amount of healthy skin removed is determined by the location and the thickness of the melanoma being treated.

While wide excision surgery is often the only treatment necessary, in some cases a doctor may also choose to check for cancer in nearby lymph nodes by performing a sentinel lymph node biopsy. If cancer cells are found in the lymph nodes, further treatment will become necessary, such as a lymph node dissection (removing nearby lymph nodes), chemotherapy, immunotherapy, or targeted therapies.

Stage II Melanoma

With stage II melanoma, the tumor has penetrated the skin deeper than 1 mm. It may have ulcerated, but not in all cases. Although a tumor at this stage may not have advanced, it has a high risk of spreading. A thicker melanoma, such as a tumor more than 4 mm, has a very high risk of spreading. 

Treatments for Stage II Melanoma

As with stage I, stage II melanoma is typically treated with wide excision surgery, which cuts out the melanoma along with a margin of healthy surrounding skin. In the case of stage II melanoma, many doctors will recommend looking for cancer in nearby lymph nodes by performing a sentinel lymph node biopsy, which may necessitate further treatment if cancer cells are found.