EVALUATION OF THE ROLE OF MUTANT IDH1, EGFR AND BCL2 PROTEIN EXPRESSION IN DISTINGUISHING DIFFUSE ASTROCYTOMA FROM ASTROCYTOSIS

Abstract

Background: Gliomas are the most relevant primary brain tumors. Diffuse astrocytomas are the most common type of gliomas .The distinction of diffuse infiltrating astrocytoma from reactive astrocytosis is one of the most difficult differential diagnosis especially with small biopsies (e.g. stereotactic biopsies). Several markers were used for this differentiation such as glial fibrillary acidic protein, ki67 and p53; but each of them has problems with sensitivity and specificity. The immunohistochemical markers such as mutant isocitrate dehydrogenase 1 (IDH1), EGFR and Bcl2 may be useful in this differentiation.
Aim: This study was conducted to clarify the value of IDH1, EGFR and Bcl2 protein expression in making a clear distinction between diffuse infiltrating astrocytomas and morphologically similar reactive astrocytosis.
Methods: Fifty representative cases; 30 cases WHO grade II diffuse astrocytomas and 20 cases of reactive conditions were examined immunohistochemically using antibodies against mutant IDH1, EGFR and Bcl2.
Results: IDH1 was positive in 60% of astrocytomas cases but it was totally absent in reactive astrocytosis. EGFR was expressed in 50% of astrocytomas; but it was not expressed in reactive astrocytosis. Bcl2 expression was detected in 56.7% of astrocytomas cases. However; it was expressed also in 75% of reactive astrocytosis cases.
Conclusion: IDH1, EGFR were the most useful IHC markers in the discrimination of low grade diffuse astrocytomas WHO II from reactive astrocytosis; particularly in small biopsies. Bcl2 play no role in this differentiation
Key words: Astrocytoma, Astrocytosis, IDH1, EGFR, BCL2