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The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on July 21, 2021.

Melanoma stages

Though melanoma is a relatively rare form of skin cancer, about 106,110 new cases are expected to be diagnosed in 2021, the American Cancer Society estimates. About 1 percent of skin cancers are melanomas—most others are basal cell and squamous cell skin cancers—but melanomas make up a majority of skin cancer deaths.

Before recommending treatment, doctors first need to learn more about the melanoma and what’s going on inside the skin.

TNM staging

The melanoma staging process can be complex. Stages are assigned based on the size or thickness of the tumor, whether or not it has spread to the lymph nodes or other organs, and certain other characteristics such as growth rate.

The stages range from 1 through 4, with higher numbers indicating more advanced melanoma. Some stage numbers are followed by the capital letters A through D to further describe the tumor and its potential spread.

The American Joint Committee on Cancer has developed a uniform staging system that allows doctors to determine how advanced a melanoma is, and to share that information with each other in a meaningful way.

This melanoma staging system, known as TNM staging, measures three characteristics of the cancer.

T (tumor): Describes the tumor’s thickness, or how deep it has grown into the skin. The thickness of the melanoma, also known as the Breslow measurement, is an important factor in predicting whether or not a tumor has spread. The thicker the melanoma, the greater the chance of it spreading. The rate at which the tumor cells are dividing (also known as the mitotic rate) and the presence or absence of ulceration (an open, bleeding sore) are also considered in determining the T category.

N (node): Indicates whether or not the melanoma has spread to nearby lymph nodes, or the channels connecting the lymph nodes.

M (metastasis): Refers to whether or not the melanoma has spread to distant organs, as well as on levels of lactate dehydrogenase (LDH), a substance in the blood. In other words, if it has metastasized.

The TNM categories also have subtypes.

Tumor thickness (T)

  • TX: Main tumor can’t be measured
  • T0: Main tumor can’t be found
  • Tis: Melanoma in situ (abnormal cells found in the outer layer of the skin, or epidermis)
  • T1: ≤1.0 mm
  • T2: >1.0-2.0 mm
  • T3: >2.0-4.0 mm
  • T4: >4.0 mm

Lymph node involvement (N): The higher the number after the N, the more lymph nodes that contain cancer.

  • NX: Cancer in nearby lymph nodes can’t be measured
  • N0: No cancer in nearby lymph nodes
  • N1-N3: Refers to the number of lymph nodes that contain cancer

Metastasis (M): Melanoma may spread almost anywhere, but it tends to travel to the lungs, liver, brain, bones and the skin or lymph nodes in other parts of the body. The letter M indicates the potential spread of the melanoma throughout the body.

  • MX: Spread can’t be measured
  • M0: Cancer hasn’t spread to other parts of the body
  • M1: Cancer has spread to other parts of the body

Melanoma stages

Once doctors have collected all the information they can about the cancer, they will assign a stage. The stage gives doctor and patient a common language to understand how advanced the cancer is, where it’s located and which treatment options are available.

  • Stage 0: This is also called melanoma in situ. It means that there are melanocyte cells that may turn cancerous on your skin. This is the earliest stage—it’s best to catch and treat melanocytes here before they have the chance to turn cancerous.
  • Stage 1: In general, a stage 1 melanoma has grown deeper into the skin but hasn’t spread to the lymph nodes or other parts of the body.
    • With stage 1A, the cancer isn’t more than 1 mm thick, with or without ulceration.
    • With stage1B, the tumor is more than 1 mm thick, but not more than 2 mm thick, without ulceration.
  • Stage 2: A stage 2 melanoma has grown deeper into the skin and has more high-risk features, but it hasn’t spread yet.
    • With stage 2A, the tumor is either more than 1 mm but not more than 2 mm thick, with ulceration, or more than 2 mm but not more than 4 mm thick, without ulceration.
    • In stage 2B, the tumor is more than 2 mm but not more than 4 mm thick, with ulceration, or more than 4 mm thick, without ulceration.
    • In stage 2C, the tumor is more than 4 mm thick, with ulceration. A melanoma with a thickness greater than 4 mm has a high risk of spreading.
  • Stage 3: A stage 3 melanoma diagnosis means that the cancer cells have spread to nearby lymph nodes, but not to distant organs or any other part of the body.
    • Stage 3 is divided into 3A, 3B, 3C and 3D. These letters reflect the extent and degree of growth into the lymph nodes.
  • Stage 4: In stage 4, the melanoma has spread to other organs and/or distant lymph nodes.
    • Though it all falls within stage 4 cancer, the M of the TNM system may indicate where the cancer has spread specifically, such as to other areas of the skin (M1A), the lung (M1B), other organs or areas of the body (M1C), or—at its most advanced—the central nervous system (M1D).

Clinical staging and pathologic staging

To add to the complexity of staging, the cancer also may have a clinical stage and a pathologic stage.

Clinical staging takes place before surgery, based on blood tests, physical exams or imaging tests such as X-rays, a computed tomography (CT) scan, magnetic resonance imaging (MRI) or positron emission tomography (PET) scans.

What doctors discover during surgery may provide more detailed information about the cancer’s size and spread. Often, some tissue from the surgery will be examined afterward to provide more clues. This process is known as pathologic staging, or surgical staging.

If surgery isn’t possible, doctors will use the clinical stage when determining a treatment plan.

Recurrent melanoma cancer

A relapse of melanoma within 2 cm of the original tumor site is considered a local recurrence. Lymph node recurrence and distant recurrence are terms used to describe cancer that has the same DNA characteristics as the original tumor but develops elsewhere in the body, such as the lymph nodes.

Lymph node recurrence develops in the lymph node(s) in the area nearest the original melanoma tumor. It’s considered distant recurrence when melanoma cells enter the bloodstream and develop into tumors at another location in the body. Once they enter the circulatory system, melanoma cancer cells may travel to distant sites. They may develop in any tissue, but they typically grow in the lungs, liver or brain. Metastases may also occur in the bone, heart, pancreas, kidneys or thyroid, among other locations.