Renal angiomyolipoma with inferior vena cava tumor thrombus in a pregnant woman.

Renal angiomyolipoma (AML) is a benign mesenchymal tumor that rarely shows aggressive behavior, like vascular invasion. Venous invasion of AML into the inferior vena cava (IVC) is extremely rare, especially in pregnancy, where both diagnosis and treatment are further complicated by maternal and fetal factors. We present the case of a 27-year-old pregnant woman incidentally diagnosed with bilateral renal AMLs, including a right-sided lesion with tumor thrombus extending into the intrahepatic IVC. This diagnosis was made using multiple imaging modalities: ultrasound, magnetic resonance imaging, and postpartum computed tomography. Imaging confirmed macroscopic fat within the tumors and delineated the extent of vascular involvement. Per patient decision, she was closely monitored during pregnancy, then underwent a successful open right radical nephrectomy and IVC thrombectomy postpartum. This case highlights the crucial role of imaging in detecting rare aggressive behavior in an otherwise benign tumor and shows the importance of multidisciplinary planning to prevent more serious complications.