Abstract
INTRODUCTION: Retroperitoneal tumors account for 0.2% of all neoplasms. Among these tumors, retroperitoneal vascular malformations are particularly rare, with most previously reported cases being venous malformations. CASE PRESENTATION: A 72-year-old woman was diagnosed with a retroperitoneal tumor on abdominal computed tomography. The 27-mm diameter tumor was located away from the right kidney and major vessels in the right perirenal adipose tissue. Contrast-enhanced computed tomography revealed a heterogeneously enhanced tumor with well-defined borders. Dynamic contrast-enhanced magnetic resonance imaging revealed rapid enhancement in the arterial phase and a progressive filling-in pattern in the delayed phase. Although vascular malformation was suspected, a definitive diagnosis could not be established. The retroperitoneal tumor was excised laparoscopically for therapeutic and diagnostic purposes, and the histopathological diagnosis confirmed it as a capillary arteriovenous malformation. CONCLUSION: Herein, we presented a rare case of retroperitoneal capillary arteriovenous malformation that was difficult to definitively diagnose preoperatively.