Renal Endometriosis Mimics Renal Cell Carcinoma in a Hypoplastic Kidney: A Case Report

Renal endometriosis is a rare disorder of cases of urinary tract endometriosis. A 42-year-old woman presented at our outpatient department with an incidental painless mass on her left hypoplastic kidney revealed on an abdominal ultrasound. Abdominal and pelvic examinations revealed no abnormal findings. A computed tomography (CT) scan revealed an anterolateral slightly enhanced left renal mass that measured 1.2 cm in diameter. Furthermore, CT did not reveal any evidence of abdominal or thoracic metastasis. There are a few case reports in the literature of tumors in specimens from patients who underwent nephrectomy for hypoplastic kidneys, but discriminating between benign and malignant masses is difficult unless a nephrectomy is performed. Given the radiological findings and the impaired function of the hypoplastic kidney, laparoscopic radical nephrectomy was recommended. The procedure was performed under general anesthesia without intraoperative or postoperative complications. Microscopic examination revealed several findings consistent with a diagnosis of renal endometriosis. The patient had no symptoms at her last followup visit. This case highlights that renal endometriosis can mimic renal cell carcinoma and awareness of this entity should be raised, as it can be asymptomatic, especially when located in a hypoplastic kidney.