Immunohistochemical analysis of MIB-1 proliferative activity in human endometrial cancer. Correlation with clinicopathological parameters, patient outcome, retinoblastoma immunoreactivity and K-ras codon 12 point mutations.

To test the prognostic utility of MIB-1 in human endometrial neoplasias, the proliferative activities of fifty-two endometrial carcinomas obtained from Polish women were assessed. We also investigated the relationship between the MIB-1 Proliferative Index and the well-known clinicopathological features of cancer (clinical stage, histological type, histological grade, depth of myometrial invasion), patient's age, overall survival, retinoblastoma immunostaining and K-ras codon 12 point mutations. The mean MIB-1 Proliferation Index was 43.8%, with a median of 36.0%. Due to the great intratumour heterogeneity of the immunoreaction, the Index ranged from 0% to 98%. A significant relationship was noted between MIB-1 expression and histological grading (p = 0.0004) and myometrial invasion of cancer (p = 0.01). Multivariate Cox regression demonstrated that the clinical stage was the only independent prognostic factor during follow-up (p = 0.025). There was a tendency towards a poorer outcome for women with a Proliferative Index of > 31% than for patients whose Index was < or = 31%; the difference, however, did not reach significance (p = 0.25; log-rank test). Interestingly, uterine cancers lacking retinoblastoma protein expression had a mean MIB-1 Proliferation Index that was nearly twice as high as in those neoplasias that stained positively for retinoblastoma (70.33% and 42.14%, respectively; p = 0.09; Mann-Whitney-U test). There were no significant differences between K-ras codon 12 point mutation-positive and -negative endometrial carcinomas regarding the proliferative activity of the cancer (mean Indexes 47.6% and 43.8%, respectively; p = 0.66, Mann-Whitney-U test). Our data support the view that MIB-1 proliferative activity was significantly increased with a decrease of the histological grading and with the myometrial invasion of human endometrial cancer.