Melanoma Skin Cancer Stages

After someone is diagnosed with melanoma, doctors will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

The earliest stage melanomas are stage 0 (melanoma in situ), and then range from stages I (1) through IV (4). Some stages are split further, using capital letters (A, B, etc.). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter means a lower stage. Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

The staging system most often used for melanoma is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

The extent of the main (primary) tumor (T): How deep has the cancer grown into the skin? Is the cancer ulcerated?

  • Tumor thickness: The thickness of the melanoma is called the Breslow measurement. In general, melanomas less than 1 millimeter (mm) thick (about 1/25 of an inch) have a very small chance of spreading. As the melanoma becomes thicker, it has a greater chance of spreading.
  • Ulceration: Ulceration is a breakdown of the skin over the melanoma. Melanomas that are ulcerated tend to have a worse outlook.

The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?

The spread (metastasis) to distant sites (M): Has the cancer spread to distant lymph nodes or distant organs ? (Melanoma can spread almost anywhere in the body, but the most common sites of spread are the lungs, liver, brain, bones, and the skin or lymph nodes in other parts of the body.)

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced. Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more information, see Cancer Staging.

The staging system in the table below uses the pathologic stage (also called the surgical stage). This is determined by examining tissue removed during an operation. Sometimes, if surgery is not possible right away (or at all), the cancer will be given a clinical stage instead. This is based on the results of physical exams, biopsies, and imaging tests (as described in Tests for Melanoma Skin Cancer). The clinical stage will be used to help plan treatment. Sometimes, though, the cancer has spread farther than the clinical stage estimates, so it may not predict a person’s outlook as accurately as a pathologic stage. If your cancer has been clinically staged, it is best to talk to your doctor about your specific stage.

The table below is a simplified version of the most recent TNM system, effective as of 2018.

Melanoma staging can be very complex, so if you have any questions about the stage of your cancer or what it means, ask your doctor to explain it to you in a way you understand.

AJCC Stage

Melanoma Stage Description

0

The cancer is confined to the epidermis, the outermost skin layer (Tis). It has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). 

This stage is also known as melanoma in situ.

I

 

The tumor is no more than 2mm (2/25 of an inch) thick and might or might not be ulcerated (T1 or T2a). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0)

 

II

The tumor is more than 1 mm thick (T2b or T3) and may be thicker than 4 mm (T4). It might or might not be ulcerated. The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).

IIIA

The tumor is no more than 2 mm thick and might or might not be ulcerated (T1 or T2a). The cancer has spread to 1 to 3 nearby lymph nodes, but it is so small that it is only seen under the microscope (N1a or N2a). It has not spread to distant parts of the body (M0).

 

IIIB

 

There is no sign of the primary tumor (T0) AND:

  • The cancer has spread to only one nearby lymph node (N1b) OR
  • It has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor (without reaching the nearby lymph nodes) (N1c)

It has not spread to distant parts of the body (M0).

OR

The tumor is no more than 4 mm thick and might or might not be ulcerated (T1, T2, or T3a) AND:  

  • The cancer has spread to only one nearby lymph node (N1a or N1b) OR
  • It has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor (without reaching the nearby lymph nodes) (N1c) OR
  • It has spread to 2 or 3 nearby lymph nodes (N2a or N2b)

It has not spread to distant parts of the body (M0).

IIIC

There is no sign of the primary tumor (T0) AND:

  • The cancer has spread to 2 or more nearby lymph nodes, at least one of which could be seen or felt (N2b or N3b) OR
  • It has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor, and it has reached the nearby lymph nodes (N2c or N3c) OR
  • It has spread to nearby lymph nodes that are clumped together (N3b or N3c)

It has not spread to distant parts of the body (M0).

OR

The tumor is no more than 4 mm thick, and might or might not be ulcerated (T1, T2, or T3a) AND:

  • The cancer has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor, and it has reached nearby lymph nodes (N2c or N3c) OR
  • The cancer has spread to 4 or more nearby lymph nodes (N3a or N3b), or it has spread to nearby lymph nodes that are clumped together (N3b or N3c)

It has not spread to distant parts of the body (M0).

OR

The tumor is more than 2 mm but no more than 4 mm thick and is ulcerated (T3b) OR it is thicker than 4 mm but is not ulcerated (T4a).

The cancer has spread to one or more nearby lymph nodes AND/OR it has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor (N1 or higher).

It has not spread to distant parts of the body.

OR

The tumor is thicker than 4 mm and is ulcerated (T4b) AND:

  • The cancer has spread to 1 to 3 nearby lymph nodes, which are not clumped together (N1a/b or N2a/b) OR
  • It has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor, and it might (N2c) or might not (N1c) have reached 1 nearby lymph node)

It has not spread to distant parts of the body (M0).

IIID

The tumor is thicker than 4 mm and is ulcerated (T4b) AND:

  • The cancer has spread to 4 or more nearby lymph nodes (N3a or N3b) OR
  • It has spread to nearby lymph nodes that are clumped together (N3b)
  • It has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor, AND it has spread to at least 2 nearby lymph nodes, or to lymph nodes that are clumped together (N3c) OR

It has not spread to distant parts of the body (M0).

IV

The tumor can be any thickness and might or might not be ulcerated (any T). The cancer might or might not have spread to nearby lymph nodes (any N). It has spread to distant lymph nodes or to organs such as the lungs, liver or brain (M0).

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

American Joint Committee on Cancer. Melanoma of the Skin. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017: 563-585.

National Comprehensive Cancer Network (NCCN). Practice Guidelines in Oncology: Cutaneous Melanoma. Version 2.2019. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/cutaneous_melanoma.pdfon June 11, 2019.

Last Medical Review: August 14, 2019 Last Revised: August 14, 2019

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