COMPARISON OF DIFFERENT KI67 ANTIBODIES IN HUMAN GLIOBLASTOMAS

Aims--To compare immunostaining between the original Ki67 monoclonal a ntibody and a new polyclonal Ki67 antibody on frozen and paraffin wax sections of human glioblastomas. Methods-- Frozen sections and formali n fixed, paraffin wax embedded sections of the same tumour specimens w ere included in the study (10 cases). Half of the paraffin wax section s were pretreated in a microwave oven. Standard immunohistochemical te chniques were used (avidin-biotin peroxidase complex). Five high power fields were examined using an eyepiece graticule, and 500 to 2000 tum our cells were counted. The labelling index was defined as the percent age of positive tumour cells. Results--The Ki67 monoclonal antibody di splayed positive immunostaining in all frozen sections (median labelli ng index 5.9, range 2.6-11.4) whereas only four paraffin wax sections stained positively and only after pretreatment in a microwave oven. Th e polyclonal Ki67 antibody elicited positive staining in both frozen s ections (median labelling index 13.7, range 6.7-21.5) and in paraffin wax sections (median labelling index 12.0, range 2.2-22.7) but only af ter pretreatment in a microwave oven. Conclusion--The Ki67 monoclonal antibody is not recommended for use on paraffin wax sections of glioma tissues whereas the new polyclonal Ki67 antibody provides satisfactor y immunostaining on both frozen and paraffin wax sections.