Figures 1-A and 1-B: Axial STIR images demonstrate a large T2 hyperintense lesion in the posterior right hepatic lobe (1-A) and a smaller T2 hyperintense lesion in the right hepatic lobe with a target appearance (1-B).

Figures 2-A and 2-B: Axial pre-contrast VIBE images demonstrate that the large lesion in the posterior right hepatic lobe (2-A) and the smaller target lesion in the right hepatic lobe (2-B) are T1 hypointense in the periphery and surround a heterogeneous T1 hyperintense central area.

Figures 3-A and 3-B: Axial contrast enhanced VIBE images during the arterial phase demonstrate that both right hepatic lobe lesions have an ill-defined peripheral rim of enhancement.

Figures 4-A and 4-B: Axial contrast enhanced VIBE image during the portal venous phase demonstrates that the large lesion in the posterior right hepatic lobe has peripheral nodular enhancement with complex internal enhancement (4-A). The smaller lesion in the right hepatic lobe (4-B) demonstrates peripheral
filling in of contrast.

Figures 5-A and 5-B. Axial contrast enhanced VIBE images during the equilibrium phase demonstrate slightly more enhancement within both right hepatic lobe lesions compared with the portal venous phase (Figures 4-A and 4-B).

Hepatic epithelioid hemangioendothelioma.

Hepatic epithelioid hemangioendothelioma (EHE) is a rare, malignant, slow-growing tumor of vascular origin. This vascular tumor also occurs in soft tissues (epithelioid hemangioendothelioma of soft tissue), bone, lung (intravascular bronchioloalveolar tumor, IVBAT), and in the spleen. Hepatic EHE differs from infantile hemangioendothelioma, which most often presents before 6 months of age and regresses spontaneously. Hepatic EHE most often occurs in middle-aged patients with a mean age of 45 years and has a female predominance. The clinical signs and symptoms EHE are nonspecific and may include abdominal pain, weakness, anorexia, jaundice, and hepatosplenomegaly. Many patients are asymptomatic and their tumors are discovered incidentally. The etiology and risk factors leading the hepatic EHE are unknown. These tumors have variable malignant potential, ranging between that of benign cavernous hemangiomas and malignant angiosarcoma. Most patients with hepatic EHE survive 5-10 years after diagnosis, reflecting this tumor’s moderate malignant potential.

EHE is described as a solid tumor of vascular origin that consists of variable proportions of epithelioid round cells and dendritic spindle cells within a fibrous myxoid stroma. Because this tumor originates from endothelial cells, the key to diagnosis of this tumor is to demonstrate cells containing factor VIII-related antigen, which is found in 97.5% of patients with EHE. These tumors demonstrate progressive sclerosis, hyalinization, and calcification in up to 50% of patients. With progression of the disease, the hepatic EHE nodules often coalesce, as they grow, usually in the periphery of the liver resulting in diffuse disease. Because hepatic EHE replaces liver parenchyma slowly over years, compensatory enlargement of uninvolved portion of the liver can be seen. The portal vein invasion can lead to portal hypertension in advanced cases. Because of the pleomorphism, the pathological diagnosis hepatic EHE can be difficult. Hepatic EHE can easily be confused at pathologic examination with cholangiocarcinoma or metastatic carcinoma.

Because the histopatholocial features of hepatic epithelioid hemangioendothelioma can be difficult, the imaging findings are an important for diagnosis and differentiating hepatic EHE from other hepatic tumors. Depending on the stage of disease, hepatic EHE can manifest as either multiple, nodular lesions or as large masses. The peripheral location EHE in the liver is characteristic. These tumors are subcapsular and do not protrude from the hepatic surface, unlike other large peripheral tumors. Capsular retraction, caused by a fibortic reaction by the EHE tumor, centered over a peripheral mass is highly suggestive of hepatic EHE. Other pathologic entities to consider that can cause a similar capsular retraction include biliary obstruction causing liver atrophy and peripheral metastatic lesions treated with chemotherapy.

On MRI, hepatic EHE tumor nodules are generally subcapsular and can be extensive. They appear moderately low signal on T1-weighted images. A thin, darker peripheral rim may be present. On T2-weighted images these tumors can demonstrate a moderately hyperintense or heterogeneous signal intensity. A dark peripheral rim may also be present on T2-weighted images. T2-weighted images can also demonstrate three concentric layers of signal intensity: a central hyperintense area, a hypointense midzone, and a moderately hyperintense peripheral rim. On gadolinium enhanced MR images, hepatic EHE lesions can demonstrate three concentric layers of alternating intensity: a central hypointense region, an enhancing peripheral rim, and an outermost hypointense rim. Differentiation of hepatic EHE from metastatic cancer, cholangiocellular carcinoma, and abscess is important, because the prognosis in hepatic EHE is significantly better than with other malignancies.

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