Determining the Stages of Melanoma

The TNM Staging System

The TNM System (Tumor-Node-Metastasis) is the most widely used way of determining cancer stages. This staging system, created by the American Joint Committee on Cancer (AJCC), provides important prognostic and survival information. A number of clinical and pathological factors determine the stage of melanoma.

Learn the factors for staging melanoma

T for Tumor

The “T” categories are given numbers (0 to 4) based on the tumor’s thickness. The tumor may also be assigned the letter “a” or “b” based on ulceration and mitotic rate.

  • TX: Tumor cannot be evaluated.
  • T0: Zero evidence of cancer.
  • Tis: Melanoma is “in situ” meaning it is still in the outer layer of skin and has not grown into other layers, and shows no signs of spreading.
  • T1: The primary tumor is 1.0mm or thinner and one of the following:
    • T1a: There is no ulceration and the mitotic count is less than 1mm2.
    • T1b: There is ulceration or the mitotic count is equal to or greater than 1mm2.
  • T2: The primary tumor’s thickness is between 1.01mm and 2.0mm and one of the following:
    • T2a: There is no ulceration.
    • T2b: There is ulceration.
  • T3: The primary tumor’s thickness is between 2.01mm and 4.0mm and one of the following:
    • T3a: There is no ulceration.
    • T3b: There is ulceration.
  • T4: The primary tumor is thicker than 4.0mm and one of the following:
    • T4a: There is no ulceration.
    • T4b: There is ulceration.

N for Nodes

The “N” classification tells you if melanoma cells have moved from the primary tumor into nearby lymph nodes. Melanoma cells that are found along the lymphatic vessel but have not yet entered a lymph node are called “in-transit metastases” or “satellites.” The number of lymph nodes to which the cancer has spread is important. When more lymph nodes have melanoma, there is reason for greater concern.

  • NX: Regional (in the area near the melanoma primary site) lymph nodes cannot be evaluated.
  • N0: No evidence of spread to the lymph nodes.
  • N1: The melanoma has spread to 1 lymph node and one of the following:
    • N1a: The doctor cannot feel cancer in the lymph nodes but can detect the cells when a sample is taken (microscopic metastasis).
    • N1b: The doctor feels cancer in the lymph node or can see it on a scan (macroscopic metastasis).
  • N2: Melanoma has spread to 2 or 3 lymph nodes and one of the following:
    • N2a: The doctor cannot feel a tumor in the lymph nodes but can see melanoma cells in a lymph node sample under the microscope (microscopic metastasis).
    • N2b: The doctor can feel the tumor in the lymph nodes or see it on a scan (macroscopic metastasis).
    • N2c: The doctor finds in-transit metastases or satellites without finding metastatic nodes.
  • N3: Any of the following conditions:
    • The melanoma has spread to 4 or more lymph nodes.
    • Two or more lymph nodes appear joined together (called matted lymph nodes).
    • In-transit metastases or satellites are present, with any number of metastatic lymph nodes.

M for Metastasis

The “M” classification tells you if melanoma cells have moved from the primary (original) site to distant sites in the body, and where in the body they have moved to. The seriousness of the melanoma depends on where it has spread (metastasized). Usually, metastasis is associated with more advanced stages of cancer.

  • MX: Distant metastasis cannot be evaluated.
  • M0: The melanoma has not spread to distant sites.
  • M1a: The melanoma has spread outside the region where it first started to other parts of the skin, under the skin, or any distant lymph nodes.
  • M1b: The melanoma has spread to the lungs.
  • M1c: The melanoma has spread to any other internal organ in the body other than the lungs and the LDH is normal OR there is distant spread to any site and the LDH is elevated.

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