oncolex logo
Utskriftsdato 5.7.2020

Staging of malignant melanoma

TNM Classification

For skin melanoma, the TNM classification is used (13) for staging.

The TNM system describes the anatomical extent of the disease at presentation. “T” refers to the extent of the primary tumor. “N” (node) refers to the absence or presence and extent of regional lymph node metastasis. “M” refers to the absence or presence of distant metastasis.

The TNM classification differentiates between clinical classification (TNM) and pathology classification (pTNM). The staging is performed after removal and then according to pTNM.

pTNM classification

pT classification of melanoma is based on three criteria:

  • Thickness of the tumor (Breslow), the largest vertical diameter of the tumor in millimeters.
  • Mitoses
  • Ulceration of primary tumor present or not 


  • pTX – primary tumor cannot be assessed 
  • pT0 – no evidence of primary tumor
  • pTis – melanoma in situ


  • pT1 – tumors 1 mm or less in thickness
    • pT1a – without ulceration and mitoses <1/mm²
    • pT1b – with ulceration or mitoses ≥1/mm² 


  • pT2 – tumors from 1,01 mm - 2 mm in thickness
    • pT2a – without ulceration
    • pT2b – with ulceration


  • pT3 – tumors from 2,01 mm - 4 mm in thickness
    • pT3a – without ulceration
    • pT3b – with ulceration


  • pT4 – tumors more than 4 mm in thickness
    • pT4a – without ulceration
    • pT4b – with ulceration


  • NX – regional lymph node cannot be assessed 
  • N0 – no regional lymph node metastasis 


  • N1 – metastasis in regional lymph node
    • N1a – only microscopic metastasis (clinically occult)
    • N1b – macroscopic metastasis 


  • N2 – metastasis in two or three regional lymph nodes, satellites or in-transit metastasis
    • N2a – only microscopic metastasis
    • N2b – macroscopic metastasis
    • N2c – satellites or in-transit metastasis without lymph node metastasis


  • N3 – metastases in four or more regional lymph nodes, or coalescing metastatic regional lymph node, or the combination satellite-/in-transit metastasis and lymph node metastasis


  • MX – distant metastasis cannot be assessed
  • M0 – no distant metastasis 
  • M1 – distant metastasis 
    • M1a – distant metastasis in skin, subcutanous tissue or lymph nodes outside regional lymph nodes  
    • M1b – lung metastases
    • M1c – metastasis in other sites, or any site and an elevated serum lactate dehydrogenase (LDH)

Mucous membrane

Stage I  Localized disease
Stage II Regional lymph node metastases
Stage III Distant metastases