Cyst of Hattori: A Rare Cyst in the Posterior Mediastinum

Sixteen years since their initial description in the literature, posterior mediastinal Mullerian cysts - otherwise known as cysts of Hattori, after their discoverer - remain rare, with only 40 patients reported as of 2020. We report a 43 year old obese female that presented with a 2.6 cm cyst found in the posterior mediastinum by endoscopic ultrasound (EUS) and previously by chest magnetic resonance imaging (MRI) originally diagnosed as a congenital enteric duplication cyst of the esophagus radiologically. Upon surgical excision via a DaVinci thoracoscopy, the cyst was confirmed to be of Mullerian origin by PAX8, WT1, and ER staining. It is possible that the majority of cysts of Hattori remain unrecognized and undiagnosed, given their rarity and resemblance to other pathologies. It is important that this entity become a part of every pathologist's differential for a posterior mediastinal cyst in a female.