Ectopic decidual reaction in the urinary bladder presenting as a vesical tumor

A urinary bladder tumor in young pregnant women is a very rare finding. It may bring diagnostic problems despite use of advanced imaging techniques. We report on a case of an exceedingly rare occurrence of a decidual reaction in the urinary bladder of a pregnant young woman. To the best of our knowledge, it is the first such case reported in published medical data. The final diagnosis was possible only after histopathologic assessment of a specimen obtained during diagnostic cystoscopy, which showed typical decidual changes within detrusor muscle, without ectopic endometrium, which could suggest more frequent vesical endometriosis.