Although hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the human liver, the molecular changes and mechanisms that regulate its development and progression remain unclear. In the present study, we investigated the correlation between beta-catenin expression and clinical outcome in 51 patients with relatively small (maximal diameter < 30 mm), solitary HCCs. The tumors were classified according to histological tumor differentiation (grade I, 11 tumors; grade II, 28

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... mors; grade III, 12 tumors). Using immunohistochemical methods to detect nuclear accumulation of beta-catenin, we investigated the correlation between beta-catenin expression and clinical outcome and compared the correlation with cyclin D1, Ki-67, and E-cadherin. Focal or generalized nuclear beta-catenin expression was observed in 36.4% (4 of 11) of the grade I tumors, 39.3% (11 of 28) of the grade II tumors, and 25% (3 of 12) of the grade III tumors. Nuclear beta-catenin-positive grade III tumors were associated with significantly poorer survival (P = 0.004), whereas none of the patients with nuclear beta-catenin-negative grade I tumors died. With regard to proliferative activity, positive nuclear beta-catenin staining correlated significantly with an increased Ki-67 labeling index in grade I (P < 0.0001) and grade III (P = 0.0045) tumors and with reduced epithelial cadherin expression in the cell membrane (P < 0.001). In contrast, no association with the expression of cyclin D1, one of the target factors of beta-catenin, was detected. Our present data suggest that beta-catenin plays important roles in promoting tumor progression by stimulating tumor cell proliferation and reducing the activity of cell adhesion systems and is associated with a poor prognosis, especially in patients with poorly differentiated HCCs.