Question

Explain what is the Tumor, Node, and Metastases (TNM) staging system. Discuss whether the following classification for a patient with a metastasized tumor is possible: T4, N0, M1. Explain your answer.

Answer 1

TNM staging is a system to describe the amount and spread of cancer in a patient’s body.

In the TNM system:

• The T refers to the size and extent of the main tumor. The main tumor is usually called the primary tumor which is considered as the site of origin.
• The N refers to the the number of nearby lymph nodes in which cancer is detected.
• The M refers to whether the cancer has metastasized. This means that the cancer has spread from the primary tumor to other parts of the body.
• The TNM staging system for all solid tumors was devised by Pierre Denoix between 1943 and 1952, using the size and extension of the primary tumor, its lymphatic involvement, and the presence of metastases to classify the progression of cancer.

Mandatory parameters-

• T: size or direct extent of the primary tumor
  • Tx: tumor cannot be assessed
  • Tis: carcinoma in situ
  • T0: no evidence of tumor
  • T1, T2, T3, T4: size and/or extension of the primary tumor
• N: degree of spread to regional lymph nodes
  • Nx: lymph nodes cannot be assessed
  • N0: no regional lymph nodes metastasis
  • N1: regional lymph node metastasis present; at some sites, tumor spread to closest or small number of regional lymph nodes
  • N2: tumor spread to an extent between N1 and N3
  • N3: tumor spread to more distant or numerous regional lymph nodes
• M: presence of distant metastasis
  • M0: no distant metastasis
  • M1: metastasis to distant organs (beyond regional lymph nodes)
  • MX: Metastasis cannot be measured.

T4N0M1 would mean that metastasis has occured without nodal involvement. This is oossible in few carcinomas and most of sarcomas whose main mode of spread is via haematological route. In these cases cancer cells may avoid getting trapped in the lymph nodes and reach a distant site without causing lymph node involvement.