Complicated renal angiomyolipoma with renal vein fat embolism mimicking lipid-rich renal cell carcinoma: A case report

Renal angiomyolipoma (AML) is a benign renal tumor that may rarely present with intratumoral hemorrhage or fat-containing venous extension, creating diagnostic overlap with lipid-rich renal cell carcinoma (RCC). A middle-aged man presented with acute right flank pain and hematuria. Clinical evaluation and laboratory tests were unremarkable apart from microscopic hematuria, and no syndromic features were identified. Computed tomography demonstrated a fat-containing right renal mass with hemorrhage and a fat-density filling defect in the distal renal vein. Magnetic resonance imaging confirmed macroscopic fat within the lesion and venous extension. Ultrasound-guided biopsy revealed classic triphasic AML supported by HMB-45, Melan-A, and smooth muscle actin positivity. Given hemodynamic stability and biopsy confirmation, conservative management was chosen. Follow-up computed tomography at 3 months showed reduction in tumor size and resolving hemorrhage. Multimodality imaging and biopsy are essential to distinguish complicated AML from lipid-rich renal cell carcinoma and to guide appropriate, individualized management.