The American Joint Committee on Cancer TNM system is used in staging breast cancer. Tumor (T) is followed by a number 1-4 based on tumor size and spread to the chest wall or skin. Node (N) is followed by a number 1-3 based on spread to axillary lymph nodes/number of abnormal lymph nodes. Metastasis (M) is followed by 0 or 1 based on spread to distant organs.

After TNM staging, breast cancers are further staged into groups with similar treatment/prognosis (Stage 0 to IV, with many subdivisions within each). Stage 0 is assigned to in situ disease. Stage I tumors are small +/- micrometastasis to axillary lymph nodes. Stage II tumors are larger +/- spread to up to 3 local lymph nodes. Stage III tumors have either invaded into up to 10 local lymph nodes or into the chest wall. Stage IV tumors have spread to distant organs/lymph nodes.

(Breastcancer.org stages 2015)

MALIGNANT BREAST DISORDERS:

Staging and Prognosis