Medulloblastoma: evaluation of proliferative index by monoclonal antibody Mib-1, its prognostic correlation and therapeutic implications

In the past few years, the monoclonal antibody MIB-1 has been used by researchers in order to retrospectively study paraffin imbibed tumor fragments. The medulloblastoma is the most common malignant central nervous system tumor in childhood. The objectives were: determination of the mean Mib-1 LI value from these patients, as well as the prognostic value of the method.This retrospective study represents an analysis of the cellular proliferation index of posterior fossa medulloblastomas collected from 22 patients at A.C. Camargo Hospital, from January 1990 to December 1999. The histopathological diagnosis was confirmed by H&E and proliferative index (LI) was achived with Mib-1 which detects proliferating cells during G1, G2, S and M phases.The results demostrated that the mean Mib-1 was 30,1%, and ranged from 5,2% to 62,0%.In conclusion, this method has prognostic value, has to be used as routine for patients harboring medulloblastomas and the ones who have PI greater than the mean value found in this study, should be treated aggressively.

A critical reappraisal of MIB-1 labelling index significance in a large series of pituitary tumours: secreting versus non-secreting adenomas.

Pituitary tumours are usually benign neoplasia, but may have a locally aggressive or malignant evolution. This study aimed to identify factors which mostly influence their proliferative activity, in order to clarify its value for clinical and research purposes. The proliferative index was determined in a prospective series of 132 pituitary tumours as the percentage of monoclonal antibody MIB-1-immunopositive cells and referred to as the MIB-1 labelling index (LI). Its distribution was analysed according to both univariate and multivariate models. A life-threatening pituitary tumour is presented separately. The mean LI was 1.24+/-1.59%, with significant differences between clinically secreting (CS) and clinically non-secreting (CNS) adenomas. In CS adenomas (n=65), LI was highly variable and markedly influenced by pre-operative pharmacological treatment (0.80+/-1.03 vs 2.06+/-2.39% in treated vs untreated cases, P=0.009); it decreased with patient's age (P=0.025, r=0.28) and increased with tumour volume and invasiveness. The influence of pre-operative treatment and macroscopic features on LI in this group was confirmed by multivariate analysis. In CNS adenomas (n=67), LI distribution was less variable than in CS adenomas (P<0.0001), it was age-independent and correlations with tumour volume, invasiveness or recurrence did not reach significance. In a rapidly growing parasellar tumour, the mean LI was 24% at first surgery and exceeded 50% at second surgery performed 4 months later. LI should be interpreted according to hormone secretion and pre-operative treatment. Unusually high LI values deserve particular attention.