A 52-year-old post-menopausal woman undergoes biopsy of a breast lump. Histology shows malignant cells arranged in single-file rows (Indian file pattern) and targetoid periductal infiltration. Tumor cells are E-cadherin negative. The diagnosis is:
- A Invasive ductal carcinoma, NOS
- B Invasive lobular carcinoma ✓
- C Medullary carcinoma of the breast
- D Mucinous (colloid) carcinoma
Correct answer: B. Invasive lobular carcinoma
Explanation
Invasive lobular carcinoma (ILC) is characterized by loss of E-cadherin (CDH1 mutation/silencing), causing cells to lose cohesion and infiltrate stroma in single-file (Indian file) rows and around ducts (targetoid pattern). It can be bilateral and multicentric. Invasive ductal carcinoma NOS shows varied patterns but maintains E-cadherin; medullary carcinoma has a syncytial growth pattern with lymphocytic infiltrate; mucinous carcinoma has cells floating in mucin pools.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.