Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 6 4 2021 11 27 150 154 Hedieh Moradi Tabriz Department of Pathology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran. elham nazar Department of Pathology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran. Arezoo Eftekhar Javadi Hospital 2020 09 01 2020 09 29 Introduction: Extrarenal angiomyolipoma is an uncommon disease entity and is rare in the retroperitoneum. This lesion shows three benign components, including mature adipose tissue, thick-walled blood vessels, and smooth muscles. Case Report: This report describes a 37-year-old woman who presented with incidental right retroperitoneal mass in prenatal checkup. The patient underwent excisional surgery. Histological examinations and the immunohistochemical study revealed angiomyolipoma. Based on the diagnosis, the patient received no more treatment. After 3 years of close follow- up examinations, no recurrence was observed. Conclusion: This diagnosis is often confused with many other entities in retroperitoneum. Thus, imaging and histologic correlation are required. Proper diagnosis is essential for further patient management and avoids unnecessary treatment. https://crcp.tums.ac.ir/index.php/crcp/article/view/403