Immunohistochemical assessment of the MIB-1 Labeling Index in human hepatoblastoma and its prognostic relevance.

BACKGROUND/PURPOSE: The MIB-1 monoclonal antibody has been raised against recombinant parts of the Ki-67 antigen, which is a cell cycle-related nuclear protein that is elevated in late G1 and S phases. The aim of the study was to analyze the expression pattern of MIB-1 in hepatoblastoma and to assess whether it provides any prognostic information in clinical practice. METHODS: Sections from formalin-fixed paraffin embedded tissues were collected from 18 patients who had hepatoblastoma and stained with MIB-1 antibody according to streptavidinbiotin method. A percentage score of positively stained nuclei, MIB-1 Labeling Index (LI), was determined and correlated with clinical variables. MIB-1 LI ranged from 0% to 39.5% with a mean value of 13.5%. Among them in 14 patients, who received preoperative chemotherapy, the authors analyzed the result of MIB-1 staining. RESULTS: Although there were no significant correlations between MIB-1 LI and age, sex, or histological type, a statistically significant correlation was found between clinical stage and MIB-1 LI. Mean MIB-1 LI was lower in patients with stage I and II than in those with stages III and IV (P < .05). Metastatic lesions showed higher MIB-1 LI than primary lesions, indicating that metastatic tumor cells have an increased rate of cellular proliferation. Kaplan Meier survival curve showed that patients with MIB-1 higher than 10% (n = 3) had a worse survival rate than those with lower than 10% MIB-1 LI (n = 11), whereas there was no significant difference because of the limited number of cases. Because high MIB-1 LI was correlated with clinical stage and poor survival rate, MIB-1 LI may be considered an important prognostic factor in hepatoblastoma. CONCLUSION: Although further studies, including larger series of patients, are required, the authors consider MIB-1 immunostaining an easy method to assess proliferative activity that provides useful prognostic information in hepatoblastoma.