Intrathyroidal Branchial Cleft Cyst Mimicking Malignancy: A Cytologic Pitfall in the Era of Incidental Imaging

Branchial cleft cysts are congenital anomalies derived from the branchial apparatus, most commonly presenting as lateral neck masses. Intrathyroidal localization is exceedingly rare and may mimic malignancy both radiologically and cytologically—particularly when squamous cells are identified and misinterpreted as malignant. Surgical resection is often required to achieve a definitive diagnosis. Our report highlights the diagnostic challenges of such lesions and underscores the importance of integrating clinical, cytological, and imaging data.