Extrarenal Wilms tumor in the retroperitoneum of a 6-year-old girl: a case report and review of the literature

IntroductionExtrarenal Wilms tumor is an extremely rare condition, typically documented only in isolated case reports. Unlike classical intrarenal Wilms tumors, extrarenal Wilms tumors arise outside the kidney, often presenting a diagnostic challenge owing to its unusual location and overlapping features with other retroperitoneal tumors. Its rarity necessitates further documentation to improve recognition and management. This report presents a case of extrarenal Wilms tumor located in the retroperitoneal space of a 6-year-old girl.Case presentationA 6-year-old white Iranian girl presented with abdominal pain and swelling in the upper left abdomen. Physical examination revealed a firm, nontender, immobile mass. Ultrasound imaging identified a well-defined mass with significant necrotic and cystic areas. Abdominopelvic computed tomography scan showed a large mass on the left side of the abdomen, exerting pressure on the adjacent pancreas, spleen, and left kidney. The patient underwent laparotomy and received 19 weeks of chemotherapy, including actinomycin-D and vincristine. Post-treatment, she fully recovered and underwent monthly sonography follow-ups for 6 months after completing chemotherapy and has shown no signs of recurrence to date.ConclusionsExtrarenal Wilms tumor should be considered in the differential diagnosis of abdominal pain, especially in young children, owing to its rarity and the potential for misdiagnosis as other retroperitoneal tumors. A definitive diagnosis is made through surgical intervention followed by histopathological examination.