3.1. General information and follow up
As Table 1 shows, this study included 57 patients (25 with hemangiomas, 13 with HEHE, and 19 with HAS) with tumors derived from hepatic vascular endothelial cells. No significant differences were found with regard to age of onset (P=0.148) or sex (P=0.950) among the three patient groups. The cases of HAS were associated with liver cirrhosis(P=0.001). The liver lesions manifested mostly as masses, with proportions of 84%, 92.31%, and 78.95% for hemangiomas, HEHE, and HAS, respectively. The differences among these groups were significant (P<0.001). The average tumor diameter was significantly higher (9.13±4.20 cm, P= 0.001) in the hepatic hemangiosarcoma group than those in the hepatic hemangiomas and hepatic epithelioid hemangioendothelioma (8.60±3.60 cm and 4.28±2.06 cm, respectively) . The surgical resection rates were 100% (25/25), 92.31% (12/13), and 57.89% (11/19) for hemangioma, HEHE, and HAS, respectively. The HAS resection rate was the lowest, with a significant difference of P<0.001. The proportions of patients with hepatitis in the three groups were 8% (2/25), 38.46% (5/13), and 15.79% (3/19) for hemangioma, HEHE, and HAS, respectively (P=0.063). The survival time was tracked for 8-39 months. The 13 cases of HEHE in this study showed no lung and bone metastases during the follow up after hepatectomy. Eleven patients in the HAS group died, but no deaths occurred in the hemangioma or HEHE groups.
3.2. MRI findings
As Table 2 shows, the proportions of cases with circumscribed margins were 88% (22/25), 84.6% (11/13), and 31.6% (6/19) for hemangioma, HEHE, and HAS, respectively (P<0.001). The differences among these groups were significant, and HAS lesions were more likely to not have circumscribed margins. The proportions of lesions with hemorrhaging were 4% (1/25), 44.4% (4/13), and 36.8% (7/13) for hemangioma, HEHE, and HAS, respectively, (P=0.014). The proportions of cases with homogeneously low T1WI signals were 72% (18/25), 46.1% (6/13), and 21% (4/19) for hemangioma, HEHE, and HAS, respectively (P=0.004). HEHE and HAS were more likely to show heterogeneous signals on T1WI (Figs. 1A, 3A, and 4A). The proportions of cases with homogeneously high signals on T2WI 64% (16/25), 23.1% (3/13; Fig. 2B), and 10.5% (2/19) for hemangioma, HEHE, and HAS, respectively (P=0.001). HEHE and HAS were more likely to show heterogeneous signals on T2WI. Centripetal enhancement was the common pattern in vascular tumors, with proportions of 100%, 46.2% (6/13), and 68.4% (13/19) for hemangioma, HEHE, and HAS, respectively (Figs. 3B-3D and 4C-4E). The difference in the enhancement pattern between the HEHE and HAS groups was significant（P<0.001）, and rim enhancement was common in cases of HEHE (46.2%, 6/13; Figs. 1C-1E, 2C-2E). In addition, three cases of HAS (15.8%, 3/19) showed no enhancement in any of the phases.
3.3. Microscopic observations
Hemangiomas showed tumor tissues composed of many thin-walled and anastomosing blood vessel lumens. The lumens contained blood, and the vessel walls were vascular endothelial cell monolayers. Cells were typical, with local interstitial hyperplasia and blood vessel deformation due to compression.
In the HEHE group, the tumor tissue centers showed large collagen connective tissues and mucus matrices, with many epithelioid tumor cells (some of which were imprinted-like) and small vascular lumens rich in red blood cells (RBCs). In the tumor tissue, a few residual hepatocyte cords and small bile ducts were observed, with no capsule in the periphery area. The hepatic sinusoids in the neighboring liver tissues showed tumor cell growth, and the hepatic lobule structure was normal. Capsules were observed on the edges of a few HEHE cases (2/13, 15.4%). The immunohistochemistry results were as follows: HeP-1(-), CK18(+), CK19(-), CD24(-), β-Catenin(+), CA199(-), P53(+), CD31(+), and CD34(+).
In the HAS group, tumor cells were solid and arranged in a fissure-like structure, forming a local vascular cavity-like structure. The lumens were irregular and anastomosing. Some vascular lumens were broken and invaded the liver tissue with large hemorrhages. Tumor cells were obviously atypical, showing pathological nuclear mitotic figures. The immunohistochemistry results were as follows: CD31(+), CD34(+), Vimentin(+), CK(-), CK8(-), CK7(-), hepatocyte(-), AFP(-), Actin(-), Desmin(-), and S-100(-).