What is the TNM (tumor, node, metastasis) staging system for melanoma?

Updated: Jun 28, 2021
  • Author: Jonathan B Heistein, MD; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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pTX - Primary tumor cannot be assessed

pT0 - No evidence of primary tumor

pTis - Melanoma in situ; involves only epidermis (CL I)

pT1 - Tumor 1 mm or less in thickness; invades papillary dermis (CL II) (or to papillary-reticular dermal interface (CL III) (pT1b can mean that either the melanoma is ≤ 1 mm with ulceration or is < 1 mm but is Clark level IV or V with or without ulceration.)

pT2 - Tumor 1.01-2 mm in thickness

pT3 - Tumor 2.01-4 mm in thickness

pT4 - Tumor greater than 4 mm in thickness and/or invades subcutaneous tissue (CL V) and/or satellite(s) within 2 cm of the primary tumor

pT4a - Tumor greater than 4 mm in thickness with or without ulceration

Any Ta - Not ulcerated

Any Tb - Ulcerated

Regional lymph nodes (N)

  • NX - Regional lymph nodes cannot be assessed

  • N0 - No regional lymph node metastasis

  • N1 - Metastasis in 1 lymph node

  • N2 - Metastasis in 2-3 lymph nodes or spread of melanoma in the skin toward a nearby lymph node area

  • N3 - Metastasis in 4 or more lymph nodes or spread of melanoma in the skin toward a lymph node area and into the lymph node(s)

  • Any Na - Melanoma only seen under the microscope

  • Any Nb - Melanoma in the lymph node visible to naked eye

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