Proliferative potential in pituitary adenomas: measurement by monoclonal antibody MIB-1

The proliferative potential of 45 pituitary adenomas was compared with their biological behaviour as determined by immunohistochemical studies, radiological findings, and clinical manifestations. The PCI (proliferating cell index) as measured using antibody MIB-1 in this study ranged from 0.05 to 4.80%, with an average PCI of 1.49 +/- 0.19% (mean +/- standard error of the mean). There was no significant correlation between proliferation and hormonal state, maximum size, intra-adenomatous haemorrhage, or invasiveness. However, a PCI > or = 1.5% appeared to correlate with the likelihood of tumour regrowth (regrowth rate: 50%); for PCIs < 1.5%, the rate was 16%. Regrowth adenomas had a higher mean MIB-1 PCI than non-regrowth adenomas [2.34 +/- 0.58% (SE) versus 1.14 +/- 0.16%, p < or = 0.05]. MIB-1 PCIs may provide information that is useful for planning follow-up studies and treatment after surgical resection.