Understanding Melanoma Staging

Your melanoma stage will be determined twice: 

• After the biopsy
  
  • This is called clinical staging when you find out you have melanoma.
  • Clinical staging helps guide treatment decisions.
• After surgery
  
  • This is called pathological staging.
  • Pathological staging is more accurate because it includes all information available about your melanoma and can guide further treatment decisions.

Below, we provide pathological staging information.

Melanoma staging is currently based on the 8^th edition (2018) American Joint Committee on Cancer (AJCC) staging system that uses clinical and pathological information to assign stage based on three features: tumor, node, and metastasis. When considered together, this is called the Tumor-Node-Metastasis (TNM) approach. The TNM system uses information from the primary tumor (T category - tumor), the extent of spread to draining lymph nodes or other regional sites (N category - nodal), and the presence or absence of spread to distant sites (M category – metastasis) such as lung, liver, or brain. Using these factors, a stage group is assigned based on estimates of survival and is frequently used as the basis for treatment recommendations, discussions of prognosis, and clinical trial options.

T category

‍In melanoma that arises in the skin, the T category refers to how deeply the primary (original) tumor has grown into the skin and is measured in millimeters (mm). This is also called the Breslow depth. For melanoma, tumor size does not refer to the width of the lesion on the skin.

• Tis, melanoma in situ.
• T1, ≤1 mm.
• T2, more than 1 mm and up to 2 mm.
• T3, more than 2 mm and up to 4 mm.
• T4, >4 mm.

The T1 category is further broken down into “a” and “b”:

• T1a refers to a melanoma that is <0.8 mm thick without ulceration. Ulceration is when the skin is broken due to the tumor.
• T1b refers to a melanoma that is <0.8 mm thick with ulceration OR 0.8-1 mm thick with or without ulceration. 

The T2, T3, and T4 categories are also further broken down into “a” and “b” depending on whether or not the tumor is ulcerated. For example:

• T2a refers to a melanoma that is more than 1 mm and up to 2 mm thick without ulceration.
• T2b refers to a melanoma that is more than 1 mm and up to 2 mm thick with ulceration.

N category

‍This refers to whether regional, or nearby, draining lymph nodes are positive for cancer, as well as whether melanoma has spread to skin or soft tissue between the primary tumor and the regional lymph nodes, called in-transit, satellite, or microsatellite metastases.  

• N0, no regional metastases.
• N1, one cancer-positive regional lymph node OR in-transit, satellite, and/or microsatellite metastases without regional lymph node involvement.
• N2, two or three cancer-positive regional nodes OR in-transit, satellite, and/or microsatellite metastases with one positive node.
• N3, four or more cancer-positive regional nodes OR in-transit, satellite, and/or microsatellite metastases with two or more positive nodes OR any number of matted nodes (groups of lymph nodes that have become stuck together, forming a single mass) without or with in-transit, satellite, and/or microsatellite metastases.

As shown in the table below, the N category also has “a,” “b,” and “c” designations depending on whether the positive lymph node(s) were detected by sentinel lymph node biopsy (SLNB) or clinically (meaning by physical exam—they can be felt) and the presence or absence of in-transit, satellite, and/or microsatellite metastases.

M Category

This describes the spread of the melanoma (also called metastasis) throughout the body to distant sites such as the brain, liver, lungs, gastrointestinal tract, or other places.

• M0, no evidence of distant metastasis.
• M1, evidence of distant metastasis.  

The M1 category also has “a,” “b,” “c,” and “d” designations depending on where the cancer has spread.

• M1a melanoma has spread to the skin, soft tissue including muscle, and/or nonregional lymph nodes.
• M1b melanoma has spread to the lung (with or without the sites for M1a melanoma).
• M1c melanoma has spread to other organs (for example, the liver) but not the brain or spinal cord (with or without the sites for M1a or M1b melanoma).
• M1d melanoma has spread to the brain and/or spinal cord (with or without the sites for M1a, M1b, or M1c melanoma).

Also, for each M1 designation, the lactate dehydrogenase (LDH) status is indicated with “0” for not elevated or “1” for elevated. Read more about LDH.

Combining T, N, and M Categories to Determine the Stage of Melanoma

Together, the T, N, and M categories are used to determine the stage of melanoma.

In general, the higher the stage, the more severe the melanoma. When you hear that someone has stage 3 melanoma, they are probably referring to the AJCC stage. 

This table summarizes how the T, N, and M category information helps define the pathological stage of the melanoma. Pathological staging includes information from before surgery (biopsy, clinical exam, and radiological imaging including X-rays and CT scans) plus examination of the tumor tissue and any lymph nodes removed during surgery.

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More to explore

• Melanoma Stage 0
• Melanoma Stage 1
• Melanoma Stage 2‍
• Melanoma Stage 3
• Melanoma Stage 4