Different assessments of immunohistochemically stained Ki-67 and hTERT in glioblastoma multiforme yield variable results: a study with reference to survival prognosis.

OBJECTIVE: To investigate a marker of tumor proliferation, Ki-67, and telomerase expression in glioblastoma multiforme and to compare the results of different mainly quantitative assessments, in relation to age and survival rates. METHODS: Immunohistochemical stainings of Ki-67 and hTERT were evaluated in 39 formaldehyde-fixed, paraffin-embedded surgical samples of glioblastoma multiforme diagnosed during 2004, comprising all specimens with sufficient amount of vital tissue sent to the Department of Pathology during this year. Ki-67 counting and hTERT evaluation was assessed on whole tumor sections and on selected areas within each section. Age and length of survival were analyzed in relation to these parameters. RESULTS: We found that different methods of evaluating the stained sections yielded different results regarding Ki-67, but less marked differences for hTERT. With Ki-67 counting on whole sections (non-selected areas), we found a statistically significant correlation with length of survival. There was no corresponding information in the hTERT assessment. We could also confirm a significant inverse correlation between age and length of survival, as previously published. CONCLUSION: Our data demonstrate that different methods of Ki-67 evaluation may give markedly dissimilar results. The significant correlation found between survival and one but not with two other methods of Ki-67 assessment, implicate the value of standardized quantification methods. Our data indicate a possible prognostic use of immunohistochemical Ki-67 proliferation index in glioblastoma multiforme.