GFAP and metastatic carcinoma: Immunohistochemical (IHC) stains are useful adjunct diagnostic tool: metastatic carcinomas are CKs positive but stain negatively for S-100, myxopapillary ependymomas are positive for S-100 but co-express glial fibrillary acidic protein (GFAP) while chordoid meningiomas are positive for EMA but negative for CK and GFAP4.