Melanoma Staging: What Each Diagnosis Reveals

Melanoma is the most aggressive form of skin cancer. Melanoma staging is the process that's used to determine the size of a melanoma tumor and where and how far it has spread. Melanoma is divided into stages from 0, which is the lowest stage, to IV, which is the highest stage. Staging is important because it helps your healthcare team plan the appropriate treatment. After a melanoma diagnosis, follow-up full skin examinations should be scheduled regularly.

TNM Staging of Melanoma

Healthcare professionals have come up with various methods for staging cancers. This article uses the 2009 TNM System that's recommended by the American Joint Commission on Cancer. It's the most widely used staging system in the world. 

In the TNM system, the letters T, N, and M refer to:

• T = tumor: T is followed by a number that corresponds to tumor thickness.
• N = node: N is followed by a number that corresponds to the extent of lymph node involvement.
• M = metastasis (distant spreading): M is followed by a number that corresponds to the extent of metastasis.

Your doctor may also inform you of the Clark level or Breslow depth of your melanoma. These technical terms are both measurements of how deep the tumor extends into your skin.

In addition, the "T" may be followed an "a" that signifies no ulceration, or a "b" that signifies ulceration. Ulceration, which indicates more severe disease and is identified under the microscope, occurs when melanoma invades the overlying skin.

In general, the thicker the lesion and the farther that the cancer has spread, the higher the assigned stage. The higher the stage, the worse the long-term outlook is.

Learn more about all the different stages of melanoma and what they indicate, below.

When melanoma is caught at a very early stage and it hasn't penetrated beneath the surface of the skin, it's known as melanoma in situ. It's highly curable and is either called stage 0 or it's not given a stage. Stage 0 melanomas are removed by wide excision and typically require no further work-up.  

Cure rates are excellent with surgical removal since these melanomas are least likely to have spread.

• Stage IA (T1aN0M0): The tumor has not spread to the nodes. It is less than 1 mm and is not ulcerated. Five-year survival is 95 percent.
• Stage IB (T1bN0M0 or T2aN0M0): The tumor has not spread to the nodes. The melanoma is either less than 1 mm deep with ulceration present, or between 1.01 and 2 mm deep with no ulceration present. Five-year survival is 89 percent to 91 percent.

It's worth noting that a tumor can be less than 1 mm and not be ulcerated but still not be considered Stage IA—if it has a higher Clark level of invasion. Similarly, a tumor can be T1b and less than 1 mm without ulceration if it has an advanced Clark level.

Melanomas can be cured, but the success rate lags behind that of Stage I because a small number of cancer cells may have spread to distant sites. In addition to surgery, other forms of therapy may be recommended.

• Stage IIA (T2bN0M0 or T3aN0M0): The tumor has not spread to the nodes. It is between 1.01 and 2 mm and is ulcerated, or it is 2.01 to 4 mm without ulceration. Five-year survival is 77 percent to 79 percent.
• Stage IIB (T3bN0M0 or T4aN0M0): The tumor has not spread to the nodes. It is between 2.01 and 4 mm and is ulcerated or greater than 4 mm without ulceration. Five-year survival is 63 percent to 67 percent.
• Stage IIC (T4bN0M0): The tumor has not spread to the nodes. It is greater than 4 mm and is ulcerated. Five-year survival is 45 percent.

Since the tumor has started to metastasize, the survival rate for these stages is lower than the earlier ones.

• Stage IIIA (T1a-4a, N1a-N2a, M0): The tumor is not ulcerated. It has spread to up to three nodes, but they are not enlarged. The nodal spread is evident only on microscopic examination, not on clinical examination. Five-year survival is 63 percent to 69 percent.
  • T1b-T4b, N1a-N2a: The tumor is ulcerated. It has spread to up to three nodes, but they are not enlarged. The nodal spread is evident only on microscopic examination, not on clinical examination.
  • T1a-T4a, N1b-N2b: The tumor is not ulcerated. It has spread to up to three nodes, and the nodes are enlarged because of the melanoma.
  • T1a/b-T4a/b, N2c: The tumor can be ulcerated or not. The tumor has spread to skin that's near the melanoma (satellite metastasis) or to nearby lymph channels (in transit metastasis), but the lymph nodes themselves do not contain melanoma.
• Stage IIIB: This is a complicated stage with many possible scenarios:Overall five-year survival for this stage is 30 percent to 59 percent.
  • T1b-T4b, N1b or N2b: The tumor is ulcerated. The melanoma has spread to up to three lymph nodes, which are enlarged because of the cancer.
  • Any T, N3: The tumor can be any thickness and can be ulcerated or not. The melanoma has spread to four or more nearby nodes, or there are clumped (matted) nodes with melanoma in them, or there are satellite or in-transit metastases and the cancer has spread to nearby lymph nodes.

This stage of melanoma is associated with metastasis beyond the regional lymph nodes to distant sites in the body such as the lung, liver, or brain, or to distant areas of the skin. Neither the lymph node status nor thickness is considered. Five-year survival ranges from 7 percent to 19 percent.

A Word About Survival Rates by Stage

You may feel frightened by the survival rates listed above, but keep the following in mind. Statistics are numbers, not people. They predict what the average outcome may be, but they say little about how you, as an individual, will respond to treatment. In addition, treatments are improving. Newer treatments have been approved, and more are currently being tested in clinical trials. Statistics are often several years old, and they may not reflect how someone will respond to treatment today.

As noted earlier, the treatment of melanoma depends very much on the specific stage. The following articles discuss treatment options based on stage:

• Early Stage Melanoma Treatments (Stage I and Stage II)
• Melanoma Treatment Options (Stage III and Stage IV)