[Mullerian Cyst in the Posterior Mediastinum Resected by Robot-assisted Thoracic Surgery:Report of a Case].

Mullerian cyst in the posterior mediastinum is a rare disorder. We report on the case of a woman in her 40s with a cystic nodule which is located in the right posterior mediastinum next to the vertebra at the level of tracheal bifurcation. The tumor was suggested to be cystic by preoperative magnetic resonance imaging (MRI). The tumor was resected with robot-assisted thoracic surgery. Pathology by hematoxylin-and-eosin (H&E) revealed a thin-walled cyst lined by ciliated epithelium without cellular atypia. The diagnosis of Mullerian cyst was confirmed by immunohistochemical staining which showed the positive findings for estrogen receptor (ER) and progesterone receptor of the lining cells.