Introduction. Ganglioglioma represents a rare neuroglial tumour, affecting most frequently the pediatric population and arising in the temporal lobe. Based on the Ki67 proliferation index, gangliogliomas can be divided into benign and anaplastic.
The aim of our study was to assess the interobserver variability regarding the estimation of the Ki67 index, in order to establish if such a system could have a high reproducibility.
Material and methods. The proliferative activity of 25 cases including benign and anaplastic ganglioglioma has been revised through the Ki67 marker (clone SP6). The cases have been evaluated by five different pathologists with different degrees of experience, in order to test the reproducibility. Additionally, all the cases were evaluated for immunoreactivity for CD34 (clone QBEnd/10).
Results. Out of the 25 cases included in this study, 44% of them were diagnosed as anaplastic gangliogliomas. Best interobserver agreement was noted in cases with a low Ki67 index (<5%), namely in 85.71% of all benign gangliogliomas. Cases of anaplastic ganglioglioma which had a fatal outcome featured Ki67 values ranging from 2% to 45%. In anaplastic ganglioglioma, the difference between the lowest and the highest assigned Ki67 value per case ranged from 4 to 25, with a mean value of the differences of 11.
Conclusions. Most cases of benign gangliogliomas can easily be identified through Ki67, with little interobserver variability. Similar results can be obtained for anaplastic gangliogliomas with high Ki67 values. Nonetheless, there is a small percentage of cases with relatively high Ki67 values and little reproducibility among pathologists.
Keywords: ganglioglioma, grading, anaplastic ganglioglioma.
Tiberiu A. GEORGESCU
“Carol Davila” University of Medicine and Pharmacy Bucharest
Address: Eroii Sanitari Ave. 8, Bucharest, Romania