A 42-year-old woman has a thyroid nodule biopsied. Cytology shows 'Orphan Annie eye' nuclei (ground-glass nuclei with cleared chromatin), nuclear grooves, and psammoma bodies. Which is the most likely diagnosis?

• A Follicular carcinoma of the thyroid
• B Medullary thyroid carcinoma
• C Papillary thyroid carcinoma ✓
• D Hashimoto thyroiditis

Explanation

Papillary thyroid carcinoma (PTC) is diagnosed by its nuclear cytological features: 'Orphan Annie eye' nuclei (clear, optically empty chromatin), nuclear grooves, intranuclear cytoplasmic pseudoinclusions, and overlapping nuclei. Psammoma bodies (lamellated calcified concentric structures) are present in ~40-50% of PTC. These nuclear features are sufficient for diagnosis even on FNAC, and PTC is the most common thyroid malignancy. Follicular carcinoma is distinguished by capsular/vascular invasion, not nuclear atypia. Medullary carcinoma stains for calcitonin and Congo red (amyloid stroma).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.