Misdiagnosis of asymptomatic intrathyroidal pyriform sinus fistula: a case report.

Pyriform sinus fistula is uncommon and easily misdiagnosed. Most reported cases occur in children and are associated with either acute suppurative thyroiditis or deep neck infection. Asymptomatic pyriform sinus fistula is difficult to diagnose because it can manifest as an incidental thyroid nodule with highly suspicious malignant features on ultrasonography. The patient was a 41-year-old man with asymptomatic thyroid nodules incidentally detected on ultrasonography. Surgery was performed under the suspicion of thyroid cancer. Pathology findings revealed multiple cystic walls lined by ciliated columnar cells with stratified squamous epithelial cysts in a background of inflammatory and lymphoid cells. Barium swallow examination performed 2 weeks later revealed a sinus tract measuring 1.8 cm that arose from the apex of the left pyriform sinus. The diagnosis and management of pyriform sinus anomalies are challenging. The majority of physicians, including some otolaryngologists, lack an understanding of the disease, which should be considered one of the important differential diagnoses of neck masses. Barium swallow examination, ultrasonography, computed tomography, and laryngoscopy are useful to diagnose this condition.