Intermediate filament expression in astrocytic neoplasms.

Immunohistochemical analysis of 30 paraffin-embedded astrocytic neoplasms was performed to correlate the expression of intermediate filament proteins with histologic subtype. Each tumor was studied with monoclonal antibodies to keratin, vimentin, desmin, 200-kd neurofilament protein, and glial fibrillary acidic protein (GFAP). Immunoreactivity with the anti-keratin monoclonal antibodies AE1 and AE3 was demonstrated in 24 cases (80%) including 4 of 6 (66%) well-differentiated astrocytomas (WDAs), 10 of 12 (83%) anaplastic astrocytomas (ANAs), and 10 of 12 (83%) glioblastomas multiforme (GBMs). These cases were further studied with the monoclonal antikeratin antibodies 34 beta E12 and 34 beta H11. Of the 24 AE1/AE3-positive cases, 14 (58%) reacted with 34 beta E12. None of the cases was reactive with 34 beta H11. Vimentin expression was demonstrated in 24 cases (80%), including 2 of 6 (33%) WDAs, 11 of 12 (92%) ANAs, and 11 of 12 (92%) GBMs. Coexpression of keratin and vimentin was observed in 20 cases (67%), including 2 of 6 WDAs, 9 of 12 (75%) ANAs, and 9 of 12 (75%) GBMs. Immunoreactivity with GFAP antibody was present in all 30 (100%) cases, but none of the tumors was reactive with antibodies to desmin or 200-kd neurofilament protein. These findings demonstrate that expression of both keratin and vimentin intermediate filaments is common in astrocytic neoplasms regardless of histologic grade.