A thoracic duct cyst in 10-year-old boy: The youngest case report and review of the literature

•The mediastinal thoracic duct cyst is an extremely rare cystic lesion.•This is the first child case with a thoracic duct cyst treated thoracoscopically.•Ligation of thoracic duct without fail is necessary to prevent chylothorax.

We report the youngest case with a thoracic duct cyst located just above the diaphragm that was treated with thoracoscopic resection. The cyst was observed with serial ultrasonographic examinations during his prenatal period. No interval evidence of a deleterious effect to the fetus by this cyst was observed and born by normal vaginal delivery at term. Although the boy remained clinically asymptomatic at the age of ten, surgical excision for definitive diagnosis of the cyst was undertaken. The mediastinal cyst contained milky-white chylous fluid. Pathologically, the wall was similar in structure to the thoracic duct. The mediastinal thoracic duct cyst is an extremely rare cystic lesion. The etiology may be related to a congenital or degenerative weakness in the wall of the thoracic duct. They are generally asymptomatic but may sometimes cause pressure effects on adjacent structures. Surgical resection is the treatment of choice. The thoracoscopic resection is especially advisable for the patient with a small, asymptomatic cyst. Chylothorax is the most common postoperative complication. To avoid chylothorax after the resection of a mediastinal thoracic duct cyst, identification of the communication of the cyst with thoracic duct and ligation of its inferior pedicle without fail is necessary.