The TNM system describes the extensiveness of the disease at the time of diagnosis. "T" describes the extent of the local tumor. "N" expresses whether there are metastases to lymph nodes. "M" expresses distant metastases.
TNM classification differentiates between clinical classification (TNM) and the pathology classification (pTNM).
- TX – primary tumor cannot be assessed
- T0 – not considered a primary tumor
- Tis – carcinoma in situ
- T1 – the tumor is 2 cm or less in the largest dimension
- T2 – the tumor is over 2 cm but under 5 cm in the largest dimension
- T3 – the tumor is > 5 cm in the largest dimension
- T4 – tumor is infiltrating a deep extradermal structure, for example cartilage, muscle, or bone
In cases with multiple simultaneous tumors, the disease is classified according to the largest tumor's T category with the number of other tumors in parentheses.
- NX – lymph node metastases cannot be assessed
- N0 – no regional lymph nodes
- N1 – regional lymph node metastases
- MX – distant metastases cannot be assessed
- M0 – no distant metastases
- M1 – distant metastasis