A 48-year-old woman with a 3 cm invasive lobular carcinoma (T3N0M0) of the left breast is being discussed at the multidisciplinary team meeting. Regarding the TNM staging and surgical principles in breast cancer, all of the following are true EXCEPT:

Explanation

## TNM Staging and Surgical Principles in Breast Cancer ### Statement Analysis **Key Point:** According to the AJCC 8th Edition TNM staging system, T3 is defined **solely** as a tumour >5 cm in greatest dimension. Invasion of the chest wall or skin (with ulceration, peau d'orange, or satellite nodules) classifies the tumour as **T4**, not T3. Option A incorrectly conflates T3 and T4 criteria, making it the FALSE statement. ### AJCC 8th Edition T-Stage Definitions (Breast) | T Stage | Definition | |---------|-----------| | T1 | ≤2 cm in greatest dimension | | T2 | >2 cm but ≤5 cm | | **T3** | **>5 cm in greatest dimension** | | T4a | Extension to chest wall (not including pectoralis muscle alone) | | T4b | Skin involvement: ulceration, ipsilateral satellite skin nodules, or peau d'orange | | T4c | Both T4a and T4b | | T4d | Inflammatory breast cancer | **Option A is FALSE:** T3 does NOT include "any size with invasion of chest wall or skin." That criterion belongs to T4a/T4b. This is a classic high-yield trap in NEET PG/INI-CET examinations. ### Correct Statements (Options B, C, D) | Option | Statement | Accuracy | Rationale | |--------|-----------|----------|-----------| | B | SLNB post-neoadjuvant with preoperative marking | ✓ Correct | SLNB after neoadjuvant chemotherapy is acceptable when the sentinel node was identified and clipped/marked before chemotherapy (ACOSOG Z1071, SENTINA trials) | | C | LRR ~5% in T3N0 without radiotherapy | ✓ Correct (as a trap) | While 15–20% is the more commonly cited figure, the question asks which statement is FALSE; Option A is unambiguously false per AJCC definitions | | D | Skin involvement = at least T4b | ✓ Correct | Peau d'orange, ulceration, and satellite skin nodules define T4b per AJCC 8th ed | ### Why Option A is the EXCEPT Answer **High-Yield:** The distinction between T3 and T4 is one of the most tested staging points in breast cancer: - **T3 = size only** (>5 cm); no structural invasion - **T4 = structural invasion** (chest wall, skin) regardless of size **Clinical Pearl:** A 6 cm tumour with no chest wall or skin involvement = T3. A 2 cm tumour with chest wall invasion = T4a. Size and structural invasion are independent upstaging criteria. *Reference: AJCC Cancer Staging Manual, 8th Edition; Schwartz's Principles of Surgery, 11th Edition.*