Melanoma is grouped into Stages 0-IV based on the classifications of tumor size (T), involvement of lymph nodes (N), and distant metastasis (M). The TNM (tumor, node, metastasis) classifications are further subdivided based on the thickness of the Tumor and presence of ulceration, how many and what lymph Nodes are affected, and where the melanoma has Metastasized or spread.
The T category is measured in millimeters of actual tumor thickness with T1 = #1mm, T2 = 1.01 – 2mm, T3 = 2.01 – 4mm, T4 = > 4.0 mm. If the melanoma is ulcerated, this increases the severity. Clarks’ level is important in only the T1 category since recent evidence has found thin melanomas that penetrate deeper into the skin’s layers are more virulent.
The N category is differentiated by number of regional lymph nodes that have melanoma cells (N1 = l node, N2 = 2-3 nodes, N3 = 4 or more nodes), whether or not the nodes are clinically apparent (noticeable as abnormal on physical exam or x-ray), and the presence of satellite or in-transit metastases (small nests of melanoma cells away from the primary melanoma).
The M category is classified as to whether there is distant metastasis or not (M0 = no mets, M1 = yes), and where the metastases are located in the body (M1a = skin, subcutaneous tissues or distant lymph nodes; M1b = lungs; M3 = any other site or distant spread with a high LDH level).
For example, a melanoma T2bN0M0, is an ulcerated melanoma with a thickness between 1.01-2mm that has not metastasized to the lymph nodes or a distant part of the body.
| (T)umor Category | Tumor Thickness | Ulceration | Clark’s Level |
|---|
| TX | Primary tumor cannot be accessed (ie, shave biopsy or regressed melanoma) | N/A | N/A |
| T0 | No evidence of primary tumor | N/A | N/A |
| Tis | In situ | N/A | N/A |
| T1a | #1.0 mm | Without | Level II or III |
| T1b | #1.0 mm | With | Level IV or V |
| T2a | 1.01 – 2.0 mm | Without | N/A |
| T2b | Without | With | N/A |
| T3a | 2.01 – 4.0 mm | Without | N/A |
| T3b | 2.01 – 4.0 mm | With | N/A |
| T4a | > 4.0 mm | Without | N/A |
| T4b | > 4.0 mm | With | N/A |
Note: The American Joint Committee on Cancer (AJCC) and the World Health Organization (WHO) recommend a sentinel lymph node biopsy for primary tumors >1 mm (any stage other than Tis or T1a).| (N)ode Category | Number of Involved Nodes | Clinical Status |
|---|
| NX | Regional lymph nodes cannot be accessed | N/A |
| N0 | No regional lymph node metastasis | N/A |
| N1a | Metastasis in 1 node | Clinically non-apparent (microscopic) |
| N1b | 1 node | Clinically apparent (macroscopic) |
| N2a | 2-3 nodes | |
| N2b | 2-3 nodes | Clinically apparent (macroscopic) |
| N2c | N/A | Satellite or in-transit metastasis without regional node metastasis |
| N3 | 4 or more or combo | Metastasis in $4 regional nodes OR in-transit metastasis or satellite metastasis with regional node metastasis |
| (M)etastasis Category | Metastasis | Site or Location |
|---|
| MX | Distant metastasis cannot be assessed | N/A |
| M0 | No distant metastasis | N/A |
| M1a | Yes | Skin, subcutaneous tissues, or distant lymph nodes |
| M1b | Yes | Lungs |
| M1c | Yes | Spread to all other visceral sites OR distant spread at any site combined with an elevated LDH level |
Tables adapted from American Joint Committee on Cancer, 2002.
www.cancerstaging.net/chapter.pdf In the following section, “Staging – Stages 0-IV,” is an explanation of how the TNM classification is used to determine the stage of melanoma.
