A 45-year-old woman has a lumpectomy for a breast mass. Histology shows tumor cells arranged in single-file lines ('Indian file' pattern) infiltrating the stroma, with discohesive cells and loss of E-cadherin expression. What is the most likely diagnosis?
- A Invasive ductal carcinoma (NST) — Grade 3
- B Invasive lobular carcinoma ✓
- C Tubular carcinoma
- D Mucinous (colloid) carcinoma
Explanation
Invasive lobular carcinoma (ILC) is characterized by tumor cells arranged in single-file ('Indian file') linear strands and targetoid periductal patterns due to loss of cohesion. The key molecular hallmark is loss of E-cadherin expression (encoded by CDH1), leading to cell-cell discohesion. ILC accounts for ~10-15% of invasive breast carcinomas. It is typically ER+, PR+, HER2-negative, and carries CDH1 mutations or deletions. Invasive ductal carcinoma NOS shows gland formation. Tubular carcinoma shows well-formed tubules; mucinous carcinoma shows tumor cells floating in mucin.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.