A 52-year-old woman presents three months after a motor vehicle accident with a firm, slightly irregular 2 cm lump in the left breast at the site where the seatbelt crossed. Mammogram shows clustered microcalcifications reported as suspicious for malignancy. Core biopsy reveals fat cysts lined by foamy macrophages and foreign body giant cells surrounding anucleate ghost adipocytes. What is the most likely diagnosis?
- A Granular cell tumour
- B Invasive ductal carcinoma
- C Fat necrosis ✓
- D Plasma cell mastitis
Correct answer: C. Fat necrosis
Explanation
Trauma followed by a firm lump with lipid-laden foamy histiocytes, foreign body giant cells and ghost adipocytes is classic fat necrosis. Calcifications can develop and mimic carcinoma on mammography, which is why biopsy is mandatory, but the histology here excludes invasive ductal carcinoma, which would show malignant epithelial cells infiltrating stroma rather than a histiocytic reaction around necrotic fat.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.