Endosalpingiosis of the urinary bladder: a case of probable implantative origin with characterization of benign Fallopian tube immunohistochemistry

Müllerianosis of the bladder is an infrequently described lesion consisting of multiple Müllerian-type tissues within the urinary bladder. Few previous cases of pure endosalpingiosis have been described. Here we present a 54-year-old post-menopausal female with a history of prior pelvic surgery with traumatic bladder injury, who was found to have a cystic lesion in the posterior wall of the bladder. Routine histology demonstrated cyst epithelium characteristic of endosalpingiosis. Three benign Fallopian tube specimens were obtained and stained with the relevant immunohistochemical markers for comparison. Results showed an identical immunohistochemical profile between the bladder cyst lining and the normal Fallopian tube controls. This case represents a rare instance of pure endosalpingiosis of the urinary bladder, with a likely implantative origin. This form of bladder Müllerianosis should therefore be considered within the differential diagnosis of cystic lesions of the bladder.