Which of the following correctly pairs a breast carcinoma histological subtype with its characteristic immunohistochemical or molecular profile?
- A Secretory carcinoma — ETV6-NTRK3 fusion, ER−/PR−/HER2− ✓
- B Mucinous carcinoma — triple negative (ER−/PR−/HER2−)
- C Invasive lobular carcinoma — E-cadherin overexpression
- D Metaplastic carcinoma — ER+/PR+ in majority of cases
Correct answer: A. Secretory carcinoma — ETV6-NTRK3 fusion, ER−/PR−/HER2−
Explanation
Secretory carcinoma of the breast harbors the characteristic ETV6-NTRK3 gene fusion and is typically triple-negative (ER−/PR−/HER2−), yet paradoxically carries an excellent prognosis. This fusion is the same as seen in congenital fibrosarcoma, underscoring a shared molecular pathway. Mucinous carcinoma is typically ER/PR positive; invasive lobular carcinoma is characterized by E-cadherin loss (not overexpression) due to CDH1 mutation; metaplastic carcinoma is predominantly triple-negative.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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