Immunohistochemical expression of glial fibrillary acidic protein and CAM5.2 in glial tumors and their role in differentiating glial tumors from metastatic tumors of central nervous system

Background and Objectives: Immunohistochemistry (IHC) has become an important tool in the diagnosis of metastatic brain tumors. The judicious use of a panel of selected immunostains is unquestionably helpful in diagnostically challenging cases. In our study, the best combination of immune markers useful in differentiating metastatic carcinoma from high-grade gliomas in central nervous system (CNS) are glial fibrillary acidic protein (GFAP) and cytokeratin (CK) (CAM5.2). Materials and Methods: The study was conducted on 80 cases of glial tumors including metastatic tumors to the CNS. Histopathological diagnosis was established on routine hematoxylin and eosin staining of the sections. Special IHC markers, GFAP, and CAM 5.2 were used to differentiate glial from metastatic tumors. Result: Of total 80 cases, 40 cases of astrocytic tumors, 2 cases of ependymoma, 2 cases of mixed glial tumors, and 16 cases of glioblastoma multiforme were positive for GFAP. Twelve cases of oligodendroglioma were negative for GFAP. The sensitivity of GFAP in glial tumors was statistically significant as 81.1% and specificity 100%, whereas sensitivity and specificity of CAM5.2 in metastatic tumors were 100%. Conclusion: IHC plays an important role in diagnosing tumors of CNS and markers such as GFAP and CK (CAM 5.2) are quite effective in differentiating glial tumors from metastatic tumors of CNS.