The TNM System with Breast Cancer

The TNM System is a standard system for describing the extent of a cancer's growth. It is the most common system used to stage breast cancer. The International Union Against Cancer and the American Joint Committee on Cancer developed it. Here's what the letters stand for in the TNM System:

  • T refers to the size of the tumor in the breast.
  • N tells whether the lymph nodes in the area of the breast contain cancer.
  • M tells whether the cancer has spread (metastasized) to other organs in the body, such as your bones, brain, liver, or lungs.

Numerical values, from 0 to 4, are assigned to the T, N, and M categories. Once your oncologist has determined your T, N, and M stages, this information is put together in what is called stage grouping, set by the American Joint Committee on Cancer (AJCC). The AJCC stage grouping is used to determine your overall disease stage.