Incidental paratracheal air cyst in papillary thyroid cancer patient: a case report.

Paratracheal air cyst (PTAC) is a collection of air in the right posterior side of the trachea with an uncertain etiology. We report a papillary thyroid cancer patient with a PTAC that was removed during thyroid cancer surgery. A 68-year-old woman was diagnosed with right papillary thyroid cancer with suspicion of central lymph node metastasis. She had a history of hypertension and a rear-end collision car accident 20 years prior. On computed tomography, an ovoid cyst was incidentally found in the paratracheal region at the thoracic inlet level. Emphysematous lung with an obstructive lung defect was noted without any symptoms. Bilateral total thyroidectomy with ipsilateral central compartment neck dissection was indicated for the patient. During surgery, removal of the cyst was inevitable for complete central neck dissection. Histopathologic analysis revealed an etiology of tracheal mucus sprouting through weak trachea points. No postoperative complications occurred. The patient continued on levothyroxine medication without further radioactive iodine therapy. After 6 months, follow-up ultrasound showed no evidence of recurrence. We hypothesized that obstructive lung disease with impaired lung function or trauma history might have contributed to the development of PTAC. Future studies are needed to determine if PTACs have any association with obstructive lung disease or trauma.