Differentiation in medulloblastomas: immunohistochemical study of twenty-one cases.

Twenty-one cases of medulloblastoma (MB), 20 corresponding to the classical type and 1 to the desmoplastic variant (DPM), were studied immunohistochemically with glial fibrillary acidic protein (GFAP), S-100 protein (S-100P), neuron-specific enolase (NSE) and 200-kd neurofilaments (NF) in order to assess their differentiation potential. Their respective positivities in neoplastic cells were: 42% for GFAP, 47% for S-100P, 61% for NSE and absence of NF. Isolated neoplastic cells (e.g., cells lacking processes and with scanty cytoplasm), appeared positive for neuroglial markers (GFAP and S-100P). Most cases, however, showed positive reactive neuroglial cells. NF were never found in neoplastic cells, but in trapped neuronal processes. In most cases, large numbers of cells had high positivity to NSE. Cells of lucent islands of DPM were positive for GFAP and S-100P, while Homer-Wright type rosettes showed positive only for NSE. The above results support a neuroglial differentiation in MB. NSE was considered a nonspecific marker for neuroblastic cells.