Papillary thyroid carcinoma
Summary
The most common thyroid cancer (~80%), with excellent prognosis and lymphatic spread. Classic histology: 'Orphan Annie eye' nuclei, nuclear grooves, and psammoma bodies; risk factor is childhood ionizing radiation.
Detail
Histologic hallmarks are nuclear features: empty-appearing 'Orphan Annie eye' nuclei (ground-glass), intranuclear inclusions, nuclear grooves, and psammoma bodies, with true papillae containing fibrovascular cores. Driver mutations include BRAF V600E (most common), RET/PTC rearrangements (especially radiation-induced), and NTRK rearrangements. Spread is via lymphatics to cervical nodes (vs. follicular -> hematogenous to bone/lung). Strong association with childhood head/neck radiation exposure (e.g., Chernobyl). Diagnosis is by FNA based on nuclear features alone (a follicular variant exists). Treatment: thyroidectomy +/- radioiodine; thyroglobulin used as a tumor marker for recurrence. Excellent prognosis: 10-year survival > 95%.
Sources
- First Aid for USMLE Step 1 2024
- Robbins Basic Pathology 10th ed
- Pathoma
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