In hepatocellular carcinomas, any proportion of poorly differentiated components is associated with poor prognosis after hepatectomy.

Background: Hepatocellular carcinoma (HCC) often consists of various differentiation components in a single tumor. However, the categorization of histologic grade in hepatectomy for those tumors has not been standardized. Some studies have determined the differentiation grade of the tumor according to its worst component, whereas others have determined it according to its predominant component. The present study aimed to resolve the controversy about whether the worst component or the dominant component determines the nature of the tumor, especially focusing on the presence of a poorly differentiated component (PDC).

Methods: In total, 427 hepatectomized patients with solitary HCC were divided into three groups, tumors without a PDC (NP), tumors with a PDC but dominantly consisting of non-PDC as poorly contained (PC), and tumors predominantly consisted of a PDC as poorly dominant (PD). PC was compared with PD and NP.

Results: Statistical analysis revealed that large tumors and high alpha-fetoprotein level were significantly more frequent in PC than in NP (P < 0.01 and P = 0.04, respectively), although no remarkable difference was observed between PC and PD. Both recurrence-free and overall survival rates were significantly worse in the PC and PD groups than in the NP group (PC vs. NP: P = 0.01 and P < 0.01, PD vs. NP: P < 0.01 and P < 0.01, respectively), but there was no significant difference in these parameters between PC and PD.

Conclusions: All HCC, including PDC, should be categorized as poorly differentiated HCC regardless of the predominant differentiation component.