Understanding Melanoma Staging

Melanoma staging is based on the American Joint Committee on Cancer (AJCC) staging system that uses three key pieces of information for assigning Tumor-Node-Metastasis (TNM) classifications. In 2016, the AJCC expanded its staging guidelines to incorporate additional evidence-based prognostic factors. The goal is to create a uniform staging system with the assumption that melanomas of the same stage will have similar characteristics, treatment options, and outcomes.

The higher the stage, the more severe the melanoma. When you hear that someone has Stage III melanoma, they are probably referring to the AJCC stage.

Staging is based on the progression of the tumor at the original site (sometimes referred to as the primary tumor) and the amount the melanoma has spread throughout the body. The AJCC staging system provides a common way for doctors to communicate information about a patient’s health status and is useful in determining treatment and clinical trial options.

When discussing melanoma staging, you will see references to the Tumor size, Lymph Node involvement, and Metastasis.

• Tumor Size: This describes the size of the primary (original) tumor and whether it has invaded into nearby tissue.
  • Tis, melanoma in situ.
  • T1, ≤1.0 mm.
  • T2, >1.0–2.0 mm.
  • T3, >2.0–4.0 mm.
  • T4, >4.0 mm.

• Lymph Node involvement: This describes if regional, or nearby, lymph nodes are involved.
  • N0, no regional metastases.
  • N1, one tumor-involved node or in-transit, satellite, and/or microsatellite metastases
  • N2, two or three tumor-involved nodes or in-transit, satellite, and/or microsatellite metastases with one tumor-involved node.
  • N3, four or more tumor involved nodes or in-transit, satellite, and/or microsatellite metastases with two or more tumor-involved nodes, or any number of matted nodes without or with in-transit satellite, and/or microsatellite metastases.

• Metastasis: This describes the spread of the melanoma throughout the body.
  • M0, no evidence of distant metastasis.
  • M1, evidence of distant metastasis.  

This table summarizes how Tumor Size, the number of Lymph Nodes Involved, and Metastasis (or spread) of melanoma contribute toward its stage.

Note: It is important to note that while AJCC staging is used to help understand how far the melanoma has advanced through the body, other measures known as the Breslow Depth and the Clark Level relate to the specific melanoma biopsied, and the depth or thickness of that melanoma. It is important to note that because melanoma stage and Breslow Depth or Clark Level measure different things they are not interchangeable.

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