Thymopharyngeal duct cyst: A case report of seven-year-old patient

A thymopharyngeal duct cyst is a rare benign cervical lesion in children that arises from remnants of the thymopharyngeal duct that connects the thymus and pharynx during embryonic development. These cysts are typically congenital and asymptomatic, and they are rarely diagnosed unless complications arise. Herein, we reported the case of a seven-year-old male patient who presented with a large, painless mass in the left cervical region that developed slowly over the last three months. The mass became more prominent after an upper respiratory tract infection and was followed by an episode of fainting. On clinical examination, the mass was soft, nontender, and located posteromedial to the left sternocleidomastoid muscle with no signs of inflammation. It was observed to swell during swallowing and coughing. Magnetic resonance imaging revealed a 120×55 mm multilocular cystic lesion extending from the cervical region into the mediastinum and located near the bifurcation of the carotid artery and internal jugular vein. Initially, the mass was suspected to be a hemorrhagic cystic lymphangioma, and bleomycin injection was performed after ultrasonography-guided fluid drainage of 50 mL. However, no significant reduction in size was observed on follow-up imaging. Based on the location and characteristics of the lesion, a diagnosis of thymopharyngeal duct cyst was made. Surgical resection was performed under general anesthesia, and histological examination confirmed the diagnosis. This case represents one of the largest thymopharyngeal duct cysts extending into the mediastinum, and there were no postoperative complications.