A thyroidectomy specimen from a 32-year-old woman shows diffuse lymphocytic infiltration with germinal center formation, atrophic thyroid follicles lined by cells with abundant eosinophilic granular cytoplasm, and interstitial fibrosis. Serum anti-thyroid peroxidase antibodies are strongly positive. What is the diagnosis?

• A Graves disease
• B Riedel thyroiditis
• C Subacute granulomatous thyroiditis
• D Hashimoto thyroiditis ✓

Explanation

The combination of dense lymphocytic infiltrate with germinal centers, Huerthle cell (oncocytic) metaplasia of follicular epithelium, and high anti-TPO titers defines Hashimoto thyroiditis, an autoimmune disease with strong HLA-DR5 association. Graves lacks prominent germinal centers and Huerthle change as dominant features. Subacute thyroiditis shows granulomas with giant cells around colloid, and Riedel shows dense fibrous obliteration without oncocytic change.

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

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Written and medically reviewed by the StethoPrep medical team.