Classifying and Staging Melanoma of the Skin

Staging is how physicians determine the extent of your cancer, where it’s located and whether it has spread to nearby organs or tissues or to other parts of your body. Melanoma is usually staged twice. First, your doctor considers the results of your physical exam and any imaging tests that were performed, which will help 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 the melanoma, this staging is the most accurate and is important in determining the best treatment options for your diagnosis.

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). This system uses the size and location of the tumor (T), whether cancer cells are found in nearby lymph nodes (N) and whether the cancer has metastasized, or spread, to other parts of the body (M). You will find more information about the TNM classification in Table 1.

The thickness of the primary melanoma is used to classify the melanoma in the T category. Additionally, 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).

The node (N) classification is used to describe how many lymph nodes contain melanoma cells and includes subcategories to describe the amount of cancer cells in the lymph nodes. If the cancer cells in the lymph nodes are found only with the use of 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, the spread is “macroscopic.” The results of the TNM analysis are then used to determine the overall stage of melanoma for each individual.

Table 1. TNM system for classifying melanoma

Classification Definition
Tumor (T)
T Category Thickness Ulceration status
TX Primary tumor thickness cannot be assessed.  Not applicable
T0 No evidence of primary tumor. Not applicable
Tis Melanoma in situ. Not applicable
T1 ≤ (not more than) 1.0 mm. Unknown or unspecified
  T1a < (less than) 0.8 mm. Without ulceration
  T1b < (less than) 0.8 mm.
0.8 – 1.0 mm.
With ulceration
With or without ulceration
> (more than) 1.0 – 2.0 mm. Unknown or unspecified
  T2a > (more than) 1.0 – 2.0 mm. Without ulceration
  T2b > (more than) 1.0 – 2.0 mm. With ulceration
T3 > (more than) 2.0 – 4.0 mm. Unknown or unspecified
  T3a > (more than) 2.0 – 4.0 mm. Without ulceration
  T3b > (more than) 2.0 – 4.0 mm. With ulceration
> (more than) 4.0 mm. Unknown or unspecified
  T4a > (more than) 4.0 mm. Without ulceration
  T4b > (more than) 4.0 mm. With ulceration
Node (N)
N Category Number of tumor-involved regional lymph nodes Metastases status*
NX Regional nodes not assessed. No
N0 No regional metastases detected. No
N1 One tumor-involved node or in-transit, satellite, and/or microsatellite metastases with no tumor-involved nodes.  
  N1a One clinically occult. No
  N1b One clinically detected. No
  N1c No regional lymph node disease. Yes
N2 Two or three tumor-involved nodes or in-transit, satellite, and/or microsatellite metastases with one tumor-involved node.  
  N2a Two or three clinically occult. No
  N2b Two or three, at least one of which was clinically detected. No
  N2c One clinically occult or clinically detected. Yes
Four or more tumor-involved nodes or in-transit, satellite, and/or microsatellite metastases with two or more tumor-involved nodes, or any number of matted nodes without or with in-transit, satellite, and/or microsatellite metastases.
  N3a Four or more clinically occult. No
  N3b Four or more, at least one of which was clinically detected, or presence of any number of matted nodes. No
  N3c Two or more clinically occult or clinically detected and/or presence of any number of matted nodes. Yes
* In-transit metastases occur more than 2 cm from the primary melanoma (both on the surface of the skin or below the surface of the skin) to the regional lymph nodes. Satellite metastases occur on or below the skin within 2 cm of the primary melanoma. Microsatellite metastases in the skin or in the deeper layer of the dermis near or deep within the skin of the primary melanoma is detected upon microscopic examination.
Metastasis (M)
M Category* Anatomic site LDH level
M0 No evidence of distant metastasis. Not applicable
M1 Evidence of distant metastasis. See below

Distant metastasis to skin, soft tissue including muscle, and/or nonregional lymph node. Not recorded or unspecified

Not elevated
Distant metastasis to lung with or without M1a sites of disease. Not recorded or unspecified
Not elevated

Distant metastasis to non-CNS visceral sites with or without M1a or M1b sites of disease. Not recorded or unspecified

Not elevated

Distant metastasis to CNS with or without M1a, M1b, or M1c sites of disease. Not recorded or unspecified

*Suffixes for M category: (0) LDH not elevated, (1) LDH elevated. No suffix is used if LDH is not recorded or is unspecified.


In general, your doctor may classify your melanoma into one of five stages (see Table 2):

  • Stage 0 (melanoma in situ): Melanoma cells are found between the outer layer (epidermis) and inner layer (dermis) of the skin but have not yet invaded these layers.
  • Stage I: Melanoma is either no more than 1 millimeter thick, with or without ulceration; or thicker than 1 mm but not more than 2 mm thick, without ulceration.
  • Stage II: Melanoma is at least 1 mm thick, with or without ulceration, but has not spread beyond the primary tumor (no lymph node involvement or in-transit/satellite or microsatellite metastases).
  • Stage III: Melanoma may be any thickness, with or without ulceration, and has either spread to regional lymph nodes, or melanoma in-transit, satellite and/or microsatellite metastases have been found.
  • Stage IV: Melanoma may be any thickness, with or without ulceration, and may have spread to lymph nodes and has spread to distant organs.


Table 2. Stages of melanoma

Stage T N M
0 Tis N0 M0
IA T1a
IB T2a N0 M0
IIC T4b N0 M0
IIIA T1a/b-T2a N1a or N2a M0
N1b, N1c
N1b/c or N2b
N2b, N2c, N3b or N3c
N2c or N3a/b/c
Any N ≥ N1
IIID T4b N3a/b/c M0
IV Any T, Tis Any N M1

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.


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.


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