Melanoma Skin Cancer Stages

The stage of a cancer describes how widespread it is. For melanoma, this includes its thickness in the skin, whether it has spread to nearby lymph nodes or any other organs, and certain other factors. The stage is based on the results of physical exams, biopsies, and any imaging tests (CT or MRI scan, etc.) or other tests that have been done. These are described in Tests for Melanoma Skin Cancer. The stage of the melanoma is very important in planning your treatment and estimating your prognosis (outlook).

Understanding the stage of your melanoma

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

  • T stands for the main (primary) tumor (how far it has grown within the skin and other factors).
  • N stands for spread to nearby lymph nodes (bean-sized collections of immune system cells, to which cancers often spread first).
  • The M category is based on whether the melanoma has metastasized (spread) to distant organs.

T categories

The T category is based on:

  • 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.
  • Mitotic rate: The mitotic rate is the portion of cancer cells in the process of dividing (mitosis). A higher mitotic rate (having more cells that are dividing) means that the cancer is more likely to grow and spread. The mitotic rate is used to help stage thin melanomas (T1; see below).
  • Ulceration: Ulceration is a breakdown of the skin over the melanoma. Melanomas that are ulcerated tend to have a worse outlook.

The possible values for T are:

TX: Primary (main) tumor cannot be assessed.

T0: No evidence of primary tumor.

Tis: Melanoma in situ. (The tumor is only in the epidermis, the outermost layer of skin.)

T1a: The melanoma is less than or equal to 1.0 mm thick (1.0 mm = 1/25 of an inch), without ulceration and with a mitotic rate of less than 1/mm2.

T1b: The melanoma is less than or equal to 1.0 mm thick. It is ulcerated and/or the mitotic rate is equal to or greater than 1/mm2.

T2a: The melanoma is between 1.01 and 2.0 mm thick without ulceration.

T2b: The melanoma is between 1.01 and 2.0 mm thick with ulceration.

T3a: The melanoma is between 2.01 and 4.0 mm thick without ulceration.

T3b: The melanoma is between 2.01 and 4.0 mm thick with ulceration.

T4a: The melanoma is thicker than 4.0 mm without ulceration.

T4b: The melanoma is thicker than 4.0 mm with ulceration.

N categories

The possible values for N depend on whether or not a sentinel lymph node biopsy was done.

If the sentinel node biopsy is not done, doctors use the clinical stage of the lymph nodes, which is listed below.

NX: Nearby (regional) lymph nodes cannot be assessed.

N0: No spread to nearby lymph nodes.

N1: Spread to 1 nearby lymph node.

N2: Spread to 2 or 3 nearby lymph nodes, OR spread of melanoma to nearby skin (known as satellite tumors) or toward a nearby lymph node area (known as in-transit tumors) without reaching the lymph nodes.

N3: Spread to 4 or more lymph nodes, OR spread to lymph nodes that are clumped together, OR spread of melanoma to nearby skin (satellite tumors) or toward a lymph node area and into the lymph node(s).

If a lymph node biopsy is done, the pathologic stage can be determined, in which small letters may be added in some cases:

  • Any Na (N1a or N2a) means that the melanoma is in the lymph node(s), but it is so small that it is only seen under the microscope (also known as microscopic spread).
  • Any Nb (N1b or N2b) means that the melanoma is in the lymph node(s) and was large enough to be seen on imaging tests or felt by the doctor before it was removed (also known as macroscopic spread).
  • N2c means the melanoma has spread to very small areas of nearby skin (satellite tumors) or has spread to skin lymphatic channels around the tumor (without reaching the lymph nodes).

M categories

The M values are:

M0: No distant metastasis.

M1a: Metastasis to skin, subcutaneous (below the skin) tissue, or lymph nodes in distant parts of the body, with a normal blood LDH level.

M1b: Metastasis to the lungs, with a normal blood LDH level.

M1c: Metastasis to any other organs, OR distant spread to any site along with an elevated blood LDH level.

Stages of melanoma

Once the T, N, and M groups have been determined, they are combined to give an overall stage, using 0 and the Roman numerals I to IV (1 to 4). Some stages are further divided using capital letters.

In general, people with lower stage cancers have a better outlook for a cure or long-term survival, but other factors can also come into play. The staging of melanoma can be complex, so be sure to ask your doctor if you have any questions about the stage of your melanoma.

Stage

Stage grouping

Stage description

0

Tis, N0, M0

The melanoma is still only in the epidermis (in situ) but has not spread to deeper skin layers.

IA

T1a, N0, M0

The melanoma is less than 1.0 mm thick. It is not ulcerated and has a mitotic rate of less than 1/mm2. It has not been found in lymph nodes or distant organs.

IB

T1b or T2a, N0, M0

The melanoma is less than 1.0 mm thick and is ulcerated or has a mitotic rate of at least 1/mm2, OR it is between 1.01 and 2.0 mm and is not ulcerated. It has not been found in lymph nodes or distant organs.

IIA

T2b or T3a, N0, M0

The melanoma is between 1.01 mm and 2.0 mm thick and is ulcerated, OR it is between 2.01 and 4.0 mm thick and is not ulcerated. It has not been found in lymph nodes or distant organs.

IIB

T3b or T4a, N0, M0

The melanoma is between 2.01 mm and 4.0 mm thick and is ulcerated, OR it is thicker than 4.0 mm and is not ulcerated. It has not been found in lymph nodes or distant organs.

IIC

T4b, N0, M0

The melanoma is thicker than 4.0 mm and is ulcerated. It has not been found in lymph nodes or distant organs.

IIIA

T1a to T4a, N1a or N2a, M0

The melanoma can be any thickness, but it is not ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area, but the nodes are not enlarged and the melanoma is found only when they are viewed under the microscope. There is no distant spread.

IIIB

T1b to T4b, N1a or N2a, M0

The melanoma can be any thickness and is ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area, but the nodes are not enlarged and the melanoma is found only when they are viewed under the microscope. There is no distant spread.

OR

T1a to T4a, N1b or N2b, M0

The melanoma can be any thickness, but it is not ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area. The nodes are enlarged because of the melanoma. There is no distant spread.

OR

T1a to T4a, N2c, M0

The melanoma can be any thickness, but it is not ulcerated. It has spread to small areas of nearby skin (satellite tumors) or lymphatic channels (in-transit tumors) around the original tumor, but the nodes do not contain melanoma. There is no distant spread.

IIIC

T1b to T4b, N1b or N2b, M0

The melanoma can be any thickness and is ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area. The nodes are enlarged because of the melanoma. There is no distant spread.

OR

T1b to T4b, N2c, M0

The melanoma can be any thickness and is ulcerated. It has spread to small areas of nearby skin (satellite tumors) or lymphatic channels (in-transit tumors) around the original tumor, but the nodes do not contain melanoma. There is no distant spread.

OR

Any T, N3, M0

The melanoma can be any thickness and may or may not be ulcerated. It has spread to 4 or more nearby lymph nodes, OR to nearby lymph nodes that are clumped together, OR it has spread to nearby skin (satellite tumors) or lymphatic channels (in transit tumors) around the original tumor and to nearby lymph nodes. The nodes are enlarged because of the melanoma. There is no distant spread.

IV

Any T, any N, M1(a, b, or c)

The melanoma has spread beyond the original area of skin and nearby lymph nodes to other organs such as the lung, liver, or brain, or to distant areas of the skin, subcutaneous tissue, or distant lymph nodes. Neither thickness nor spread to nearby lymph nodes is considered in this stage, but typically the melanoma is thick and has also spread to the lymph nodes.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: May 19, 2016 Last Revised: May 20, 2016

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