Inferior vena cava leiomyosarcoma mimicking an exophytic intrahepatic cholangiocarcinoma.

Inferior vena cava (IVC) leiomyosarcomas are rare smooth muscle neoplasms that account for 0.5% of adult soft tissue sarcomas. They present with nonspecific symptoms and have poor prognosis. We present a case of leiomyosarcoma arising from the retrohepatic IVC that was difficult to diagnose on imaging, showing similar characteristics to intrahepatic cholangiocarcinoma including heterogenous arterial phase enhancement and delayed enhancement on contrast-enhanced magnetic resonance imaging. Important differentiating features of IVC leiomyosarcomas on imaging include dilated IVC, imperceptible IVC lumen, and development of prominent venous collaterals. Despite this, imaging features may be similar to other retrohepatic mass etiologies so IVC leiomyosarcoma should be included in the differential diagnosis of any retrohepatic mass and biopsy should be pursued.