A 40-year-old woman undergoes thyroid surgery for a cold nodule. Histology shows follicular cells arranged in papillary fronds with fibrovascular cores. The nuclei show 'Orphan Annie eye' (clear/ground-glass) chromatin, nuclear grooves, and intranuclear pseudoinclusions. Psammoma bodies are present. Which molecular finding is most commonly identified in this tumor?
- A RET/PTC rearrangement or BRAF V600E mutation ✓
- B RAS point mutation
- C PAX8-PPARγ fusion
- D TP53 loss-of-function mutation
Explanation
Papillary thyroid carcinoma (PTC) — the most common thyroid malignancy — has the characteristic nuclear changes described (ground-glass chromatin, grooves, pseudoinclusions) and psammoma bodies. The most common molecular alterations are BRAF V600E mutation (~45–60% of cases) and RET/PTC rearrangements (~20–40%), both activating the MAPK pathway. RAS mutations are more characteristic of follicular thyroid carcinoma and follicular variant PTC. PAX8-PPARγ fusion is characteristic of follicular carcinoma. TP53 mutations are found in poorly differentiated and anaplastic thyroid carcinoma.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.