A Case of Mediastinal Paravertebral Müllerian Cyst Resected Using Robot-Assisted Thoracoscopic Surgery

Although various tumors develop in the mediastinum, mediastinal Müllerian cysts, a new category of mediastinal tumors, are rare. We report the case of a 42-year-old woman with an incidentally discovered paravertebral mass at the level of the left 5th thoracic vertebra. Chest computed tomography revealed a 14-mm paravertebral mass, and chest magnetic resonance imaging revealed a cyst. The posterior mediastinal cyst was resected using robot-assisted thoracoscopic surgery. Hematoxylin and eosin staining revealed the presence of ciliated columnar epithelium inside the cyst wall, without cytologic atypia. Immunohistochemical staining showed the presence of estrogen receptor, progesterone receptor, and paired box gene 8. The final histopathological examination revealed that the cystic mass was a Müllerian cyst.