A 58-year-old woman from Mumbai undergoes modified radical mastectomy for a 2.5 cm invasive ductal carcinoma of the left breast. Histopathology shows: tumor confined to breast tissue, 8 out of 12 axillary lymph nodes involved with metastatic disease, and no distant metastases on staging workup. Immunohistochemistry shows ER+, PR+, HER2 negative. What is the TNM stage and predicted 5-year survival?

Explanation

## TNM Staging of Breast Cancer (AJCC 8th Edition) ### T Classification (Tumor Size) **Key Point:** T staging in breast cancer is based on tumor size: - **T1:** ≤2 cm - **T2:** >2 cm and ≤5 cm - **T3:** >5 cm - **T4:** Any size with chest wall or skin involvement This patient's tumor is **2.5 cm → T2** ### N Classification (Lymph Node Involvement) **Key Point:** N staging is based on the number of involved ipsilateral axillary lymph nodes: - **N0:** No regional lymph node metastasis - **N1:** Metastasis in 1–3 axillary lymph nodes - **N2:** Metastasis in 4–9 axillary lymph nodes - **N3:** Metastasis in ≥10 axillary nodes OR infraclavicular nodes OR internal mammary nodes with axillary nodes This patient has **8 out of 12 axillary lymph nodes involved → N2** (4–9 positive nodes) ### M Classification No distant metastases on staging workup → **M0** ### Stage Grouping (AJCC 8th Edition) | Stage | TNM | Approximate 5-Year Survival | |-------|-----|-----------------------------| | Stage IIA | T0/T1 N1 M0 or T2 N0 M0 | ~85% | | Stage IIB | T2 N1 M0 or T3 N0 M0 | ~75% | | **Stage IIIA** | **T0–T2 N2 M0 or T3 N1–N2 M0** | **~65%** | | Stage IIIB | T4 any N M0 | ~45% | | Stage IIIC | Any T N3 M0 | ~40% | ### Case Analysis - Tumor size 2.5 cm → **T2** - 8 of 12 axillary nodes positive → **N2** - No distant metastases → **M0** - **T2 N2 M0 → Stage IIIA** - **Approximate 5-year survival: ~65%** **Clinical Pearl:** With 4–9 positive axillary lymph nodes (N2), the disease is classified as Stage IIIA regardless of a relatively small primary tumor (T2). This underscores the dominant prognostic weight of nodal burden in breast cancer staging (AJCC Cancer Staging Manual, 8th Edition). **High-Yield:** Hormone receptor positivity (ER+/PR+, HER2−) confers a relatively favorable biology and eligibility for endocrine therapy (aromatase inhibitors post-menopausally), but does not alter the anatomic TNM stage. This patient would receive adjuvant chemotherapy, endocrine therapy, and likely radiation to the chest wall and regional nodes given extensive nodal involvement.