A thyroidectomy specimen from a 38-year-old woman with hypothyroidism shows a diffusely enlarged gland with dense lymphocytic infiltration, well-formed germinal centers, atrophic thyroid follicles lined by large cells with abundant granular eosinophilic cytoplasm, and interstitial fibrosis. The large cells lining the atrophic follicles represent:

• A Squamous metaplasia of thymic origin
• B Parafollicular C-cell hyperplasia
• C Oncocytic (Hurthle cell) metaplasia of follicular epithelium ✓
• D Papillary carcinoma with oncocytic features

Explanation

Hashimoto thyroiditis shows lymphoplasmacytic infiltrate with reactive germinal centers, atrophic follicles, and transformation of follicular epithelial cells into Hurthle cells, which are enlarged oxyphil cells packed with mitochondria. Giant cells with granulomas point to de Quervain thyroiditis, and psammoma bodies point to papillary carcinoma, so both distractors fail. The process is autoimmune, driven by Th1 cells and cytotoxic T-cell mediated destruction.

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.