Renal Endometriosis Mimicking a Malignancy—a Rare Case of Reno-Mullerian Fusion?

Endometriosis is a common gynaecological condition characterised by ectopic endometrial tissue growth beyond the uterine cavity. Urinary tract endometriosis represents only 1.2% of all cases, with renal accounting for less than 1% urinary involvement. An asymptomatic, 49-year-old, perimenopausal Irish female was found to have an incidental mass at upper pole right kidney on imaging studies. Histological analysis recommended outrule malignancy and open radical nephrectomy performed following multidisciplinary input. surprisingly revealed presence endosalpingiosis, accompanied significant smooth muscle component, which mimicked neoplasm. The aetiology remains unclear. However, given lack history absence other foci disease in this patient, together predominant phenotype, may represent case reno-mullerian fusion or displacement during gestational development.