Staging Melanoma
TNM Staging System

The TNM System (tumor-node-metastasis) is the most widely used system for cancer staging in the world. Created by the American Joint Committee on Cancer (AJCC), a distinguished group of experts from national healthcare organizations and major cancer centers around the country, the system defines cancer stage by describing:

  • T: the features of the primary tumor. The three distinguishing features are tumor thickness, mitoses, and ulceration. Tumor thickness (also known as Breslow depth) is measured in millimeters (mm).

    • 1 mm = .04 inch, or less than 1/16 inch (about equal to the edge of a penny)
    • 2 mm = between 1/16 and 1/8 inch (about equal to the edge of a nickel)
    • 4 mm = between 1/8 and 1/4 inch (about equal to the edges of two nickels)

  • N: the presence or absence of tumor spread to nearby lymph nodes

  • M: the presence or absence of metastasis to distant sites

Revised TNM Classification

This classification system was updated in 2009 by the AJCC.

T Classification Thickness Ulceration Status
Tis N/A N/A
T1 ≤ 1.0mm a: w/o ulceration and mitosis < 1 / mm2
b: with ulceration and mitosis ≥ 1 / mm2
T2 1.01-2.0mm a: w/o ulceration
b: with ulceration
T3 2.01-4.0mm a: w/o ulceration
b: with ulceration
T4 > 4.0mm a: w/o ulceration
b: with ulceration
N Classification # of Metastatic Nodes Nodal Metastatic Mass
N0 No evidence of lymph node metastasis
N1 1 node a: micrometastasis
b: macrometastasis
N2 2-3 nodes a: micrometastasis
b: macrometastasis
c: In transit metastases/satellites without metastatic nodes
N3 4 or more metastatic nodes, or matted nodes, or in-transit metastases/satellites and metastatic nodes
M Classification Site Serum LDH
M0 No evidence of metastasis to distant tissues or organs
M1a Distant skin, subcutaneous or nodal metastases Normal
M1b Lung metastases Normal
M1c All other visceral metastases
Or any distant metastases 		Normal
Elevated

Abbreviations: N/A, not applicable; LDH, lactate dehydrogenases