Differentiation in medulloblastomas and other primitive neuroectodermal tumours.

Fifty-four cases of primitive neuroectodermal tumour (PNET) including 47 medulloblastomas, were examined for evidence of neuronal and glial differentiation, using antibodies to neuron-specific enolase (NSE), neurofilament protein (NF), and glial fibrillary acidic protein (GFAP). In 30 of the cases, antibodies to vimentin, alphafetoprotein, cytokeratin, epithelial membrane antigen and lymphoid markers were also used. Most of the 47 medulloblastomas in the group were NSE positive but NF negative; about half were GFAP positive and three of them were positive for both neuronal markers and for GFAP. Vimentin was demonstrated in four cases and was not always co-expressed with GFAP. Medulloblastomas were negative for all the other markers. Supratentorial PNETs were sometimes positive with neuronal markers but were GFAP negative. The cell specificity of these markers and the interpretation of immunocytochemical findings are discussed in relation to differentiation potential in primitive neuroectodermal tumours.