[A case report of thoracic duct cyst].

A case of mediastinal thoracic duct is described. A 27-year-old female patient was referred to our hospital for abnormal finding of her chest X-ray film, which revealed a mediastinal mass. CT scan, endoscopic ultrasonography, MRI showed that the mass was cystic in the posterior mediastinum. Intra operative ultrasonography demonstrated a thin-walled ovoid cyst containing some high echoic parts inside, which suggested condensed milky fluid. The small pedicle entered the upper pole of cyst was found at surgery and the cyst contained chyle about 300 ml. Histopathological specimen of resected cyst showed a structure of thoracic duct with some lymphoid tissue. Postoperative course was smooth. The characteristic finding of ultrasonography seemed to be valuable in the diagnosis of thoracic duct cyst.