A 65-year-old woman with a history of neck irradiation in childhood presents with a 2.5 cm right thyroid nodule. Fine needle aspiration cytology (FNAC) shows the Bethesda category V (suspicious for malignancy) result with nuclear grooves, ground-glass nuclei, and intranuclear pseudoinclusions. What is the MOST likely histological type of thyroid carcinoma?
- A Follicular thyroid carcinoma (FTC)
- B Medullary thyroid carcinoma (MTC)
- C Anaplastic (undifferentiated) thyroid carcinoma
- D Papillary thyroid carcinoma (PTC) ✓
Explanation
The cytological features described — nuclear grooves, ground-glass (Orphan Annie eye) nuclei, and intranuclear pseudoinclusions — are the classic hallmarks of papillary thyroid carcinoma (PTC), which is the most common thyroid malignancy and is strongly associated with previous radiation exposure. PTC spreads via lymphatics to cervical lymph nodes. Follicular carcinoma is diagnosed by capsular/vascular invasion on histology; FNAC shows a follicular pattern and cannot distinguish benign from malignant (Bethesda III/IV), not the features described. Medullary carcinoma arises from parafollicular C-cells, produces calcitonin, and shows amyloid stroma on biopsy. Anaplastic carcinoma presents as a rapidly enlarging, hard, fixed mass in elderly patients with pleomorphic undifferentiated cells on cytology.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.