CT and MRI diagnosis of hepatic epithelioid hemangioendothelioma.
BACKGROUND
Hepatic epithelioid hemangioendothelioma (EHE) is a rare, low-grade malignant vascular tumor. Although its unusual imaging and pathologic findings are being recognized with increasing frequency, diagnosis is still difficult. This study aimed to analyze the CT and MRI features of hepatic EHE with a pathological study in order to improve the diagnostic accuracy and knowledge of this disease in daily practice.


METHODS
Nine patients with hepatic EHE confirmed pathologically underwent plain and dynamic contrast-enhanced multidetector row CT examination. Of these patients, four underwent additional MRI (plain T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), and dynamic contrast-enhanced scanning) and one had selective hepatic arteriography. The imaging findings were reviewed retrospectively together with the pathological results.


RESULTS
A total of 79 lesions, ranging from 3.0 to 44.6 mm in maximum diameter, with an average of 16.8+/-7.1 mm, were found in various segments of the liver. Thirty of the 79 lesions grew adjacent to the hepatic capsule. In the 4 patients receiving MRI, 39 lesions were found with low signal intensity on unenhanced T1WI and intermediate to high signal intensity on T2WI. The "capsular retraction" sign was found in all the 4 patients. Nine of the 39 lesions showed the "halo" sign after contrast enhancement on MRI. Of the 79 lesions (hypodense nodules) in the 9 patients shown by unenhanced plain CT, 26 were confluent. Calcification was found in 2 patients and the "capsular retraction" sign in 7. Thirty-eight of the 79 lesions demonstrated the "halo" sign after contrast enhancement on CT, and this sign was more clearly demonstrated in the portal venous phase. In one patient, selective hepatic arteriography showed patchy stain in the peripheral liver parenchyma with small vessels around them. Histology in all patients revealed proliferation of abnormal fibrous tissue and vessel-like structures scattered with irregular epithelioid cells having a signet ring-like structure. Immunohistochemically, all patients were positive for CD34, 4 were positive for CD31, and 3 were positive for factor VIII-related antigen.


CONCLUSIONS
Hepatic EHE may manifest as solitary or diffuse nodular lesions with a predilection for peripheral subcapsular growth and nodular confluence, together with the "halo" and "capsular retraction" signs. These imaging findings can help to improve the diagnostic accuracy of this rare hepatic tumor.