A 52-year-old woman from Mumbai presents with a palpable breast lump in the upper outer quadrant of the left breast. Clinical examination reveals a 3 cm firm, fixed mass with skin dimpling and ipsilateral axillary lymphadenopathy (3 palpable nodes, largest 2 cm). Mammography and core needle biopsy confirm invasive ductal carcinoma with intermediate grade (Nottingham Grade II). No distant metastases are detected on staging imaging. What is the TNM stage of this breast cancer?

Explanation

## TNM Staging of Breast Cancer **Key Point:** Breast cancer TNM staging requires assessment of tumour size (T), axillary lymph node involvement (N), and distant metastases (M). Each component is staged independently, then combined for overall stage grouping. ### T-Stage (Tumour Size) in Breast Cancer | T-Stage | Tumour Size | Definition | |---------|-------------|------------| | T0 | — | No evidence of primary tumour | | Tis | — | Carcinoma in situ (DCIS, LCIS, Paget's) | | T1 | ≤ 2 cm | Includes T1a (≤0.5 cm), T1b (0.5–1 cm), T1c (1–2 cm) | | T2 | > 2 cm and ≤ 5 cm | **Most common stage at presentation** | | T3 | > 5 cm | Large tumour | | T4 | Any size + skin/chest wall invasion | T4a (skin), T4b (chest wall), T4c (both), T4d (inflammatory) | ### N-Stage (Lymph Node Involvement) in Breast Cancer | N-Stage | Definition | |---------|------------| | N0 | No regional lymph node metastases | | N1 | **Metastases in 1–3 axillary lymph nodes** (most common nodal involvement) | | N2 | Metastases in 4–9 axillary lymph nodes OR clinically detected internal mammary nodes without axillary involvement | | N3 | ≥ 10 axillary nodes OR infraclavicular nodes OR internal mammary + axillary nodes | ### Analysis of This Case **T-Stage Assessment:** - Tumour size: **3 cm** → Falls in the range > 2 cm and ≤ 5 cm → **T2** - Skin dimpling is a sign of local invasion but does NOT automatically upgrade to T4 unless there is frank skin ulceration or invasion **N-Stage Assessment:** - **3 palpable axillary lymph nodes** → Metastases in 1–3 axillary nodes → **N1** - The largest node is 2 cm, which confirms metastatic involvement (normal axillary nodes are < 1 cm) **M-Stage Assessment:** - No distant metastases on staging imaging → **M0** **Overall TNM Stage: T2 N1 M0** **High-Yield:** The combination of T2 N1 M0 corresponds to **Stage IIIA** in the AJCC stage grouping (not Stage II, which would be T0–T2 with N0 only). This is a locally advanced breast cancer requiring multimodal therapy. **Clinical Pearl:** Skin dimpling alone (peau d'orange) indicates dermal lymphatic invasion but is NOT classified as T4 unless there is frank skin ulceration. T4 requires direct invasion of the dermis or epidermis with ulceration, or invasion of the chest wall (ribs, intercostal muscles, serratus anterior). **Mnemonic: 1-3 NODES = N1** — Remember that N1 is defined as 1–3 axillary lymph nodes; 4–9 nodes = N2; ≥10 nodes = N3.