A 40-year-old woman with Hashimoto thyroiditis develops progressive fatigue, weight gain, constipation, dry skin, and bradycardia. Thyroid biopsy performed years earlier showed which characteristic histologic feature that predicts this eventual functional outcome?

• A Diffuse follicular hyperplasia with tall columnar epithelium
• B Caseating granulomas with multinucleated giant cells
• C Colloid-filled follicles with flattened epithelium
• D Dense lymphocytic infiltrate with germinal center formation and Hurthle cell (oxyphilic) change ✓

Explanation

Hashimoto thyroiditis is characterized histologically by dense lymphoplasmacytic infiltration forming germinal centers and oxyphilic (Hurthle cell) metaplasia of follicular epithelium. This autoimmune destruction of thyroid tissue leads to hypothyroidism, which this patient now manifests clinically. Diffuse hyperplasia with tall columnar epithelium is seen in Graves disease. Caseating granulomas suggest granulomatous (de Quervain) thyroiditis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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