How is melanoma skin cancer staged?

Melanoma skin cancer staged

The stage of a cancer is a description of 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 tests are described in the section “How is melanoma skin cancer diagnosed?” 

The stage of the melanoma is very important in planning your treatment and estimating your prognosis (outlook). 

The American Joint Committee on Cancer (AJCC) TNM staging system 

A staging system is a standard way to describe how far a cancer has spread. The system most often used to stage melanoma is the American Joint Commission on Cancer (AJCC) TNM system. It can be complicated, so ask your doctor if you have any questions about the stage of your cancer. The TNM system is based on 3 key pieces of information: 

• T stands for tumor (how far it has grown within the skin and other factors). The T category is assigned a number (from 0 to 4) based on the tumor’s thickness (how far down it has grown). It may also be assigned a small letter a or b based on ulceration and mitotic rate, which are explained below.

 

• N stands for spread to nearby lymph nodes (bean-sized collections of immune system cells, to which cancers often spread first). The N category is assigned a number (from 0 to 3) based on whether the melanoma cells have spread to lymph nodes or are found in the lymphatic channels connecting the lymph nodes. It may also be assigned a small letter a, b, or c, as described below. 

• The M category is based on whether the melanoma has metastasized (spread) to distant organs, 

which organs it has reached, and on blood levels of a substance called LDH. 

There are 2 types of staging for melanoma: 

• Clinical staging is based on what is found on physical exams, biopsy/removal of the main melanoma, and any imaging tests that are done.

  

• Pathologic staging uses all of this information, plus what is found during biopsies of lymph nodes or other organs if they are done.   

The pathologic stage (determined after the lymph node biopsy) may actually be higher than the clinical stage (determined before the lymph node biopsy) if the biopsy finds cancer in new areas. Doctors use the pathologic stage if it is available, as it gives a more accurate picture of the extent of the cancer, but in many cases lymph node biopsies are not needed. 

T categories  

The T category is based on the thickness of the melanoma and other key factors seen in the skin biopsy. 

Tumor thickness: The pathologist looking at the skin biopsy measures the thickness of the melanoma under the microscope. This 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: To measure the mitotic rate, the pathologist counts the number of cells in the process of dividing (mitosis) in a certain amount of melanoma tissue. 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 prognosis.  

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 remains 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.  

The clinical staging of the lymph nodes, which is done without the sentinel node biopsy, 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). 

Following a lymph node biopsy, 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 visible 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. 

Stage grouping 

Once the T, N, and M groups have been determined, they are combined to give an overall stage, using Roman numerals I to IV (1 to 4) and sometimes subdivided using capital letters. This process is called stage grouping. In general, patients with lower stage cancers have a better outlook for a cure or long-term survival. 

Stage 0 

Tis, N0, M0: The melanoma is in situ, meaning that it is in the epidermis but has not spread to the dermis (lower layer).  

Stage IA 

T1a, N0, M0: The melanoma is less than 1.0 mm in thickness. 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.  

Stage IB 

T1b or T2a, N0, M0: The melanoma is less than 1.0 mm in thickness 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.  

Stage IIA 

T2b or T3a, N0, M0: The melanoma is between 1.01 mm and 2.0 mm in thickness and is ulcerated, OR it is between 2.01 and 4.0 mm and is not ulcerated. It has not been found in lymph nodes or distant organs.  

Stage IIB 

T3b or T4a, N0, M0: The melanoma is between 2.01 mm and 4.0 mm in thickness 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.  

Stage 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.  

Stage 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. 

Stage IIIB 

One of the following applies: 

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.  

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.  

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.  

Stage IIIC 

One of the following applies: 

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.  

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.  

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.  

Stage 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 spread to nearby lymph nodes nor thickness is considered in this stage, but typically the melanoma is thick and has also spread to the lymph nodes

1. What is cancer?
2. What is melanoma skin cancer?  
3. Melanoma skin cancers 
4. What are the key statistics about melanoma skin cancer?  
5. What are the risk factors for melanoma skin cancer? 
6.  what causes melanoma skin cancer? 
7. Can melanoma skin cancer be found early? 
8. How is melanoma skin cancer diagnosed? 
9. Magnetic resonance imaging (MRI) scan 

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