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 endometriosis accounting for less than 1% of urinary tract involvement. An asymptomatic, 49-year-old, perimenopausal Irish female was found to have an incidental mass at the upper pole of the right kidney on imaging studies. Histological analysis was recommended to outrule a renal malignancy and an open radical nephrectomy was performed following multidisciplinary input. Histological analysis surprisingly revealed the presence of endometriosis and endosalpingiosis, accompanied by a significant smooth muscle component, which mimicked a renal neoplasm. The aetiology of renal endometriosis remains unclear. However, given the lack of a history of endometriosis and the absence of other foci of disease in this patient, together with the smooth muscle predominant phenotype, this may represent a case of reno-mullerian fusion or endometrial displacement during gestational development. Similar content being viewed by others Data Availability Data sharing not applicable to this article as no datasets were generated or analysed during the current study.

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