iarjsIARJSIARJS2789-6102https://doi.org/10.47310/iarjs.2023.v03i01.008Complete Incision as a Treatment of Fetus in FetuAndhikaAjiNugrohoSuwardiFetus in Fetu (FIF) usually occurs in infants, presenting as an abdominal mass. It is a condition where a foetoid tumor is found withing the body of an infant. To minimize the negative effects of FIF, physicians need to acknowledge its diagnosis and management immediately. We report a case of a four-month-old boy presenting with an abdominal distension. From serology, it is known that the level of Alpha Fetoprotein (AFP) was >400.00 IU/mL and from abdominal ultrasonography we found a right retroperitoneal mass that pushes the right kidney inferiorly and extends to the left side. The patient underwent a surgery and the mass was resected. The gross pathology specimen measured 20 x 20 x 15 cm3. It contains partly formed appendicular bone, cranium and vertebrae. The patient's postoperative diagnosis was FIF.