Immunostaining patterns of two glia-associated
proteins,
glial fibrillary acidic protein (GFAP) and
S-100 protein (S100P), were compared using the
peroxidase-antiperoxidase (PAP) method on adjacent
paraffin sections in 100
brain tumors including 52 astroglial
tumors, 13
oligodendrogliomas, 14
ependymomas, 13
choroid plexus papillomas and 8
medulloblastomas. Most astroglial
tumors showed similar immunoreactivity for both
proteins. Fibrillary processes, however, showed a stronger and more crisp staining with anti-GFAP than with anti-S100P, whereas cell nuclei were labeled only for S100P. Focal dissociation of immunoreactivities for the two
proteins was prominent in several malignant astroglial
tumors including
giant cell glioblastoma, and in
subependymal giant cell astrocytoma. In
oligodendrogliomas, GFAP-positive neoplastic oligodendrocytes also showed immunoreactivity for S100P; a smaller number of
tumor cells were immunoreactive only for S100P, comparable to normal mature oligodendroglia. Most
ependymomas were characterized by a similar distribution of cells immunoreactive for both
proteins. In
choroid plexus papilloma, absent or only focal immunoreactivity for GFAP contrasted with diffuse labeling for S100P in all cases; this seems of value for a differential diagnosis of papillary CNS
tumors. In
medulloblastoma, some
tumor cells of a classical type were immunoreactive only for S100P; on the contrary, GFAP positive
tumor cells with sparse or absent immunoreactivity for S100P were found in
desmoplastic medulloblastomas. Similar immunoreactivities for both
proteins in most
tumors suggest a generally parallel production of both
proteins by glial
tumor cells.(ABSTRACT TRUNCATED AT 250 WORDS)