Microtubule-associated protein 2 (MAP-2) is expressed in low and high grade diffuse astrocytomas

The expression of neuronal antigens in diffuse astrocytomas has not been thoroughly evaluated. We have investigated the expression of microtubule associated protein 2 (MAP-2), synaptophysin and non-phosphorylated epitopes of neurofilament protein (NFP) by immunohistochemistry in 15 low grade diffuse astrocytomas and 15 glioblastomas. MAP-2 was strongly expressed in 97% of cases, using an antibody to both low and high molecular weight isoforms. An antibody specific to high molecular weight isoforms of MAP-2 (hmw-MAP-2) revealed weaker, focal staining in 60% of cases with greater expression in the glioblastomas (P=0.027). NFP was expressed in 50% of cases, but was generally weak and focal. There was little evidence of synaptophysin expression. We conclude that MAP-2 expression in astrocytomas is due predominantly to low molecular weight isoforms, which may be expressed in astrocytes as well as neurons. Focal expression of hmw-MAP-2 and NFP, however, suggest that neuronal antigens may be expressed, particularly in high grade astrocytomas. Immunopositivity for these antigens should not preclude the diagnosis of diffuse astrocytoma. (C) 2002, Elsevier Science Ltd. All rights reserved.