Melanoma Skin Cancer Stages: The Staging System

HumAdminDermatology & Skin Cancer Center

After a melanoma diagnosis has been confirmed, dermatologists will work to figure out if the cancer has spread and how far it has spread. The process of determining the spread is known as the staging system. The staging system can help describe how much cancer is in the body, how serious the cancer is and figure out the best way to treat it.

Melanoma stages range from stage 0, also known as carcinoma in situ, through stage IV. Within each stage, there are letters that also describe how far the cancer has spread. The lower the stage number, and the lower the letter associated with the stage, the lower the spread.

Determining the Stage

The American Joint Committee on Cancer, the AJCC, has come up with the TNM system. This system uses three key pieces of information.

First, dermatologists will look at the extent of the tumor, the T in TNM. The dermatologist will check the thickness of the tumor, called the Breslow measurement. Typically, a melanoma with a thickness of less than 1 millimeter has a very small chance of spreading. As the melanoma grows in thickness, it has a greater chance of spreading.

Another characteristic dermatologists look for when observing the tumor is ulceration. Ulceration is the breakdown of the skin over the melanoma. Once a tumor has ulcerated, the outlook becomes much worse.

The next area dermatologists look at is the lymph nodes, N, and if the cancer has spread to any nearby lymph nodes.

Finally, dermatologists will look at the spread, or metastasis, in other, more distant, areas, M.

Dermatologists will assign numbers to each of these three categories, based on their findings, and combine them in a process known as stage grouping, to assign an overall stage. The higher the numbers in a patient’s TNM categories, the more advanced the cancer is.

Dermatologists can either assign a clinical stage or a pathological stage to the cancer, depending on if there is time for surgery. Pathological stage, otherwise known as a surgical stage, is determined by examining tissue removed during an operation. This is typically the more accurate test. The clinical stage is determined through physical exams, biopsy and imaging tests.

The AJCC recently came out with a new staging system in 2017 that took effect January 2018. The new staging system is as follows:

Stage 0

Cancer is confirmed only on the outermost layer of skin and has not spread to the lymph nodes or other distant sites

Stage I

Cancer is no more than 2 mm thick, may or may not have ulcerated, and has not spread to lymph nodes of to distant sites

Stage II

Cancer is at least 1.01 mm thick but no greater than 4 mm thick, it may or may not be ulcerated and has not spread to nearby lymph nodes or to distant sites

Stage IIIA

Cancer is no more than 2 mm thick and may or may not be ulcerated. It has spread to three or less lymph nodes, but is so small that it’s only seen under a microscope and has no spread to distant sites

Stage IIIB

There are a few different ways stage IIIB can be classified:

  • No sign of the primary cancer, has spread to only one lymph node, satellite tumors in small areas of the skin or to skin lymphatic channels around the tumor but never reaching other lymph nodes and has not spread to distant sites; or
  • Cancer is no more than 4 mm thick, may or may not be ulcerated. There are satellite tumors nearby or has spread to skin lymphatic channels around the tumor, but never reaching other lymph nodes or has spread to two or three lymph nodes

Stage IIIC

Like with stage IIB, stage IIC can be classified in different ways, as well, including:

  • Cancer has spread to one or more lymph nodes or satellite tumors in small areas of the skin or to skin lymphatic channels around the tumor but never reaching other lymph nodes or has spread to any lymph nodes that are clumped together but has not spread to any distant sites in any of the above scenarios; or
  • Cancer is no more than 4 mm thick, may or may not be ulcerated and has spread to one or more lymph nodes or satellite tumors in small areas of the skin or to skin lymphatic channels around the tumor but never reaching other lymph nodes or has spread to any lymph nodes that are clumped together  but has not spread to any distant sites in any of the above scenarios; or
  • Cancer is between 2.1 and 4 mm or is thicker than 4 mm and may or may not be ulcerated, and has spread to one or more lymph nodes or satellite tumors are present or the cancer has spread to the skin lymphatic channels around the tumor without reaching the lymph nodes or has spread to lymph nodes clumped together  but has not spread to any distant sites in any of the above scenarios; or
  • Cancer is thicker than 4 mm and is ulcerated and has spread to no more than three lymph nodes or satellite tumors are present in small areas of the skin or the cancer has spread to skin lymphatic channels around the tumor but never reaching other lymph nodes but has not spread to distant sites.

Stage IIID

In stage IIID, the cancer is thicker than 4 mm and is ulcerated and has spread to four or more lymph nodes or satellite tumors are present in small areas of the skin or the cancer has spread to skin lymphatic channels around the tumor but never reaching other lymph nodes or has spread to lymph nodes that are clumped together.

Stage IV

Cancer may be any thickness in stage IV and may or may not be ulcerated. The cancer may or may not have spread to nearby lymph nodes, but it has spread to distant lymph nodes or organs such as the lungs, liver or brain.


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