A 45-year-old woman presents with a painless, diffusely enlarged, firm thyroid gland. TSH is elevated and anti-thyroid peroxidase antibodies are strongly positive. On histology, in addition to dense lymphocytic infiltrate with germinal centers, which of the following characteristic features is also seen?

• A Non-caseating granulomas with giant cells
• B Extensive keloid-like fibrosis
• C Hurthle cell (oxyphilic) metaplasia ✓
• D Psammoma bodies

Explanation

Hashimoto thyroiditis shows dense lymphocytic infiltrate with germinal centers and characteristic Hurthle cell (oxyphilic) metaplasia of follicular cells, which have abundant granular eosinophilic cytoplasm due to mitochondrial accumulation. Non-caseating granulomas are seen in subacute granulomatous thyroiditis. Keloid-like fibrosis is characteristic of Riedel thyroiditis. Psammoma bodies are a feature of papillary thyroid carcinoma.

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

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Written and medically reviewed by the StethoPrep medical team.