In our study, we did not find any significant difference between the two tumors in the background of liver cirrhosis and the tumor markers such as AFP, CEA and CA1-99. Being different from previous reports that patients with PHSs had no evidence of hepatitis or cirrhosis (8), Ten (62.5%) of 16 PHSs were positive for hepatitis or cirrhosis (18). Fourteen (73.7%) of 19 PHSCs had the background of liver cirrhosis, similar to previous reports that liver hepatitis virus infection might have relationship with the occurrence of PHSCs (5, 19). For PHSs, most of the laboratory data were not helpful in diagnosis (11, 15). Less than half of the patients with PHSCs were positive for AFP, which is lower than that in the ordinary HCC.
Similar to previous study (3, 12, 13, 20), the PHSCs and PHSs demonstrate hypovascularity probably for hemorrhage, necrosis, fibrous tissue or myxoid degeneration (21–24). However, the AP enhancement and dynamic enhancement pattern were significantly different. The current study concluded that PHSCs mainly showed ring hyper-enhancement on the AP, followed a washout on the later phase. It was reported that the diverse tissue compositions of PHSC determine its enhancement pattern (6). The PHSCs, especially the S-HCCs, were characterized by the peripheral viable cancerous tissue (viable cells, higher microvascular densities and relatively less fibrous tissue) and central necrosis. The sarcomatous component consists of poorly differentiated cells that grow rapidly with the neovasculature unable to adequately supply the fast-growing malignant cells, resulting in necrosis. The PHSs generally present iso-or hypo enhancement on the AP and persistent or progressive enhancement on the later phase, similar to previous studies (12, 25). The myxoid degeneration and the loose arrangement of the cells in PHSs could expand the extracellular space and the contrast agent in the extracellular space were accumulated gradually and expurgated slowly, leading to hypo-iso continuous or progressive enhancement.
Our study demonstrated the cystic mass was commonly seen in PHSs (P < 0.05). In current study, there were PHSs displaying as nearly complete cyst-like masses nearly without any enhancement simulating benign tumors, which were never seen in PHSCs. There had been an emphasis on cystic-like appearance in PHSs, which was mainly attributed to the varying degrees of myxomatous change (11, 12, 14, 26, 27). Hemorrhage also played a role in the cystic appearance, which was reported more frequently seen in PHSs than some other rare liver malignant tumors and attributed by rupture of the tumor for the serpiginous vessels (10, 11). In previous studies, there was often extensive hemorrhage in PHS creating a huge cyst mass so that the underlying tumor was obscured and misdiagnosed as a hematoma, abscess or cystic tumor (28), which also occurred in our study. Although there was not statistical difference in the current study, hemorrhage was more commonly seen in PHSs than PHSCs (50.0% vs 26.1%). Besides, the tumor larger than 10 cm in PHSs was significantly more detected than PHSCs (P < 0.05). It was reported that solid or cystic manifestations were different stages of PHSs and as the tumor grew, necrosis increased,tending to result in a cystic appearance. In summary, cystic lesions occurred more often in the PHSs and it might help us distinguish PHS from PHSCs.
The capsule invasion (19), vascular invasion or thrombosis, intrahepatic metastasis and lymph node metastasis were more prevalent in PHSCs and in our study the vascular invasion in PHSCs was close to significantly more common than the PHS (P = 0.099). The PHSCs were highly aggressive, and the presence of SC were considered to be closely related to the more invasive tumor biology, more common metastasis, low resectability and frequent postoperative recurrences (19, 29, 30). By contrast, the PHSs usually involved the adjacent anatomic structures, and vascular invasion, metastases and lymph node involvement were less common (9, 28).
These tumors should also be differentiated from other liver masses (18). The ring hyper-enhancement of PHSCs may mimic those of ICCs (31). The elevated CA19-9 levels, bile duct dilation around the lesion and capsule retraction may be helpful for the differentiation of these lesions (32). The global avid enhancement with washout and elevated AFP levels help us to differentiate the HCC from PHS and PHSC (18, 33, 34). When the PHSs displaying as nearly complete cyst-like mass as seen in our study, they should be distinguished from other cyst-like lesions such as hydatid cyst, abscess, biliary cyst and adenoma. It was reported in studies that a cyst-like PHS could be frequently misdiagnosed as a hepatic cyst (8, 14, 26). However, the presence of feeding vessels, the findings of hemorrhage and the abrupt increase in its size should alert us to the diagnosis of PHS (11, 28).
We should acknowledge several limitations to our study. First, for the retrospective study, it was technically unworkable to make the imaging-pathology match slice-by-slice. Second, the relatively small sample size had its internal disadvantages, but it was inevitable for the rare incidence of the tumors. Third, there wasn’t a recognized international standard for the evaluation of the cystic tumors.
In conclusion, the PHSC and PHS generally presented as a large subcapsular hypovascular mass. The ring hyperenhancement, wash out and more common vascular invasion favored the diagnosis of PHSC. The large mass with a diameter more than 10cm,iso-hypo intensity/density on AP and pattern of persistent or progressive enhancement might alert us to the possibility of PHS. In spite of the presence of these meaningful diagnostic features, there were not specific for the diagnosis and differential diagnosis of PHSC and PHS. However, the absence of characteristic imaging manifestations of primary hepatic tumors should remind us of the possibility of these tumors.