Staging of any cancer is done to segregate patients into risk categories that define prognosis and guide treatment recommendations for patients with similar and prognosis. Clinical breast cancer staging is performed through physical examination and imaging studies before treatment. Pathological staging is done through pathologic examination of the resected tumor and lymph nodes postoperatively.
Breast cancer staging, involves the TNM system that groups patients into four stages based on the size of the primary tumor (T), status of the regional lymph nodes (N), and presence or absence of distant metastasis (M), ranging from Stage 0 to Stage IV . Higher stage indicates more cancer spread.
The most widely used system is that of the American Joint Committee on Cancer (AJCC) Staging System. The latest AJCC Protocol Version 9 was released in January,2025 and is now available electronically. It provides a fundamental framework for clinicians in treatment decision-making, researchers in the design of future trials, and cancer registries for epidemiological studies.
A more pragmatic approach in use is to classify patients according to the treatment that they require. It groups patient as:
1. Very low-risk’ primary breast cancer,
2. ‘Low-risk’ primary breast cancer,
3. ‘High-risk’ primary breast cancer,
4. Locally advanced cancer, and 5. Metastatic cancer.
| TNM Classification of Breast Cancer | |
| T (Primary Tumor) | Criteria |
| TX | Primary tumor cannot be assessed. |
| T0 | No evidence of primary tumor. |
| Tis | Carcinoma in situ. |
| T1 | Tumor ≤20 mm in greatest dimension. |
| T2 | Tumor >20 mm but ≤50 mm in greatest dimension. |
| T3 | Tumor >50 mm in greatest dimension. |
| T4 | Tumor of any size with direct extension to the chest wall and/or to the skin. |
| N (Regional Lymph Nodes) | Criteria |
| pNX | Regional lymph nodes cannot be assessed. |
| pN0 | pN0 No regional lymph node metastasis. |
| pN1 | Micrometastases; or metastases in one to three axillary nodes and/or in internal mammary nodes with metastases detected by sentinel lymph node biopsy but not clinically detected. |
| pN2 | Metastases in four to nine axillary nodes or in clinically detected internal mammary lymph nodes in the absence of axillary lymph node metastases. |
| pN3 | Metastases in ≥10 axillary nodes; or in infraclavicular (level III axillary nodes) or in clinically detected ipsilateral internal mammary lymph nodes in the presence of one or more positive level I, II axillary nodes; or in >3 axillary lymph nodes and internal mammary lymph nodes, with micrometastases or macrometastases detected by sentinel lymph node biopsy but not clinically detected; or in ipsilateral supraclavicular lymph nodes. |
| M (Distant Metastases) | Criteria |
| M0 | No clinical or radiographic evidence of distant metastases. |
| M1 | Distant detectable metastases as determined by classic clinical and radiographic means and/or histologically proven larger than 0.2 mm. |
| Adapted from Edge SB, Byrd DR, Compton CC, et al, eds. AJCC Cancer Staging Manual. 7th ed. New York: Springer-Verlag; 2010. | |
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