Melanoma

Staging

Staging is a process to determine the extent of disease, including the size, location and whether (and where) the melanoma has spread. This information is used to categorize the melanoma into one of five main stages (0 through IV). Following your diagnosis, your doctor will use the staging information to select the best treatment options for you.

Melanoma is usually staged twice. First, your doctor will consider the results of your physical exam and any imaging tests that were done, and assign a clinical stage. Then, after a biopsy or surgical procedure, a pathologist will examine tissue taken from the tumor (and possibly nearby lymph nodes) and assign a pathologic stage. Because the pathologic stage is based on more details about your specific melanoma, this staging is more precise and is the key to deciding which treatment options may be best, and to more accurately predict the treatment outcome.

Both the clinical and pathologic stages of melanoma are classified according to the tumor, node, metastasis (TNM) system developed by the American Joint Committee on Cancer (AJCC), as shown in Table 1.

Table 1. TNM system for classifying melanoma

Tumor (T)
Tx Primary tumor cannot be assessed. 
T0 No evidence of primary tumor.
Tis
Also known as “melanoma in situ,” melanoma cells are found only between the outer layer (epidermis) and the inner layer (dermis) of skin and have not yet invaded these layers. This lesion is considered precancerous.
T1
Melanoma is no more than 1 millimeter (mm) thick (about the thickness of a credit card).
  T1a Melanoma is no more than 1 mm thick, without ulceration and a mitotic rate (the rate at which the melanoma cells are dividing and multiplying) of less than 1/mm².
  T1b Melanoma is no more than 1 mm thick, either with ulceration or a mitotic rate of 1/mm² or greater.
T2
Melanoma is thicker than 1 mm but not more than 2 mm thick.
  T2a Melanoma is thicker than 1 mm but not more than 2 mm thick, without ulceration.
  T2b Melanoma is thicker than 1 mm but not more than 2 mm thick, with ulceration.
T3 Melanoma is thicker than 2 mm but not more than 4 mm (about one-tenth of an inch) thick.
  T3a Melanoma is thicker than 2 mm but not more than 4 mm, without ulceration.
  T3b Melanoma is thicker than 2 mm but not more than 4 mm, with ulceration.
T4
Melanoma is thicker than 4 mm.
  T4a Melanoma is thicker than 4 mm, without ulceration.
  T4b Melanoma is thicker than 4 mm, with ulceration.
Nodes (N)
Nx Regional lymph nodes cannot be assessed.
N0 No melanoma found in regional lymph nodes.
N1 Melanoma found in 1 lymph node.
  N1a Microscopic metastasis found in 1 lymph node.
  N1b Macroscopic metastasis found in 1 lymph node.
N2 Melanoma found in 2-3 lymph nodes.
  N2a Microscopic metastasis found in 2-3 lymph nodes.
  N2b Macroscopic metastasis found in 2-3 lymph nodes.
  N2c In-transit melanoma or satellite lesions are found, without metastasis to lymph nodes.
N3
Melanoma is found in 4 or more lymph nodes, or in 2 or more lymph nodes that appear to be joined together (known as matted lymph nodes). Or, melanoma is found as in-transit lesions or as satellite lesions that have spread to the lymph nodes.
Metastasis (M)
Mx Metastasis cannot be assessed.
M0 No metastasis.
  M1a Metastasis to skin, subcutaneous tissues or distant lymph nodes.
  M1b Metastasis to lung.
  M1c Metastasis to any other distant organs.

 

The thickness of the primary melanoma is used to classify the melanoma in the T category. Each T classification is further divided into groups according to whether ulceration (a break in the outer layer of skin over the melanoma) is absent (subcategory a) or present (subcategory b). For example, a non-ulcerated melanoma 3 millimeters thick is classified as T3a, while an ulcerated lesion 2 mm thick is classified as T2b. Another factor for thin melanomas (those thinner than 1 mm) is the mitotic rate, which measures how fast the cancer cells are dividing and multiplying.

The node (N) classification is used to describe how many lymph nodes contain melanoma cells. The N category includes subcategories to describe the number of cancer cells in the lymph nodes. If the cancer cells in the nodes can only be found with a microscope, the metastasis (spread) is considered to be microscopic. If there are enough cancer cells in the lymph node that the doctor can feel the mass during a physical exam or can see the mass on an X-ray, it’s said to be “macroscopic” lymph node involvement. Another subcategory indicates whether melanoma has spread to the lymphatic vessels leading to a lymph node; this is known as “in-transit melanoma,” which is metastatic melanoma found between the original tumor and the nearby cluster of lymph nodes.

The metastasis (M) category is used to classify the melanoma according to whether the cancer has spread beyond the region where the melanoma started, to distant sites in the body.

Once the melanoma is classified according to the TNM system, an overall stage of disease is assigned (see Table 2). Stage 0 is known as “melanoma in situ” and is considered to be precancerous. Stage I and II melanomas are considered to be local (or localized) disease, Stage III melanoma is referred to as regional disease and Stage IV is known as distant metastatic or advanced disease.

Table 2. Stages of melanoma

Stage T N M
0 Tis N0 M0
IA T1a N0 M0
IB T1b
T2a
N0
N0
M0
M0
IIA T2b
T3a
N0
N0
M0
M0
IIB T3b
T4a
N0
N0
M0
M0
IIC T4b N0 M0
IIIA T1-T4a
T1-T4a
N1a
N2a
M0
M0
IIIB T1-T4b
T1-T4b
T1-T4a
T1-T4a
T1-T4a
N1a
N2a
N1b
N2b
N2c
M0
M0
M0
M0
M0
IIIC T1-T4b
T1-T4b
T1-T4b
Any T
N1b
N2b
N2c
N3
M0
M0
M0
M0
IV Any T Any N M1

 

Although the stage of melanoma is the main factor in determining your prognosis, it’s important to remember that prognosis by stage is based on groups of people with similar risk factors, so the prognosis for one individual may differ from that for others. Talk to your doctor about prediction tools that can help estimate your prognosis according to your specific situation.

 

Additional Resources

 

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