Clinicopathological correlation of cell proliferation, apoptosis and p53 in cerebellar pilocytic astrocytomas

We have analysed 78 cerebellar pilocytic astrocytomas to assess whether his topathology, cell proliferation, apoptosis rate, p53 immunoreactivity, or f low cytometry could predict their long-term behaviour. Classic pilocytic/mi crocystic pattern was seen in 62 patients and 16 patients had mixed pattern with an additional non-pilocytic glial component. The overall 5-year survi val was 93%, complete resection providing 100% survival. The four patients who died during the follow-up were more than 14 years of age, their primary operation had been incomplete and three of them were mixed variants. In 15 cases the tumour recurred giving a recurrence-free 5-year survival of 77%. The proliferation indices were low: Ki-67(MIB-1) (median 2.0%), PCNA (1.2% ) and S-phase fraction (4.4%). The Ki-67(MIB-1)-labelling index was signifi cantly higher in young patients, but did not differ between the classic, an d mixed variants. Twenty-two per cent of the tumours were aneuploid with a significantly higher S-phase fraction than in diploid tumours, p53 seems to act as 'guardian of the genome' in pilocytic astrocytomas, because aberran t/increased expression of p53 and aneuploidy associated with enhanced apopt osis, Only patient age (P=0.01), radicality of the primary operation (P=0.0 001) and histology (classic vs mixed, P=0.008) significantly correlated wit h survival. The poorer prognosis of the mixed variant suggests that this ma y represent a distinct entity. Although none of the novel parameters signif icantly predicted recurrence or survival, they indicate substantial biologi cal variation among cerebellar pilocytic astrocytomas.