Hepatic tumors of vascular origin: imaging appearances

A number of benign and malignant neoplasms may arise from the vascular elements within the liver parenchyma. Lesions discussed in this article include angiosarcoma, epithelioid hemangioendothelioma, solitary fibrous tumor (hemangiopericytoma), infantile, and cavernous hemangiomas. Despite a common theme of vascular origin, the pathologic and imaging appearance of these entities can be heterogeneous. Angiosarcomas are bizarrely enhancing, highly aggressive tumors, which often present with metastatic disease. When solitary, epithelioid hemangioendothelioma lesions can exhibit a concentric ring or target appearance on contrast-enhanced CT and at MR and when numerous may be indistinguishable from angiosarcoma except for a more slowly advancing course. Primary solitary fibrous tumors of the liver are exceedingly rare solid masses and most often initially diagnosed on imaging as other entities such as cholangiocarcinoma. Infantile hemangiomas consist of benign proliferation of the vascular endothelium and in the absence of flow-related complications, are usually clinically silent, and may be detected incidentally as T1 hypointense, T2 hyperintense, centripetally enhancing lesions. Cavernous hemangiomas are extremely common hepatic lesions and when classic rarely offer a challenge in diagnosis, though atypical variants may mimic more serious diseases. The purpose of this review is to provide an overview of important vascular tumors of the liver in order to aid the radiologist in providing a broad differential diagnosis for focal liver lesions, and when classic, suggest specific uncommonly seen diagnoses in order to more accurately guide clinical management.