Immunohistochemical characterization of primitive neuroectodermal tumors and their possible relationship to the stepwise ontogenetic development of the central nervous system. 1. Ontogenetic studies.

Aim of the present study was to establish different immunohistochemical staining patterns for a subsequent comparison with those of primitive neuroectodermal (PNET) subsets, i.e. PNET-NOS (not otherwise specified) or PNET with focal neuronal, astrocytic or ependymal differentiation, to relate neoplastic to embryonal development. Tissue of the developing central nervous system, with special emphasis on the stepwise development of the rhombencephalon, the cerebellar and the retinal anlage, from 20 different human embryos and fetuses ranging from 3 to 30 weeks of gestational age (GA) was examined. Six neuronal markers, synaptophysin, chromogranin A, neuron-specific enolase (NSE), neurofilament protein (NFP; 160 kDa, 200 kDa, 70 and 200 kDa) and six other markers, glial fibrillary acidic protein (GFAP), S-100 protein, vimentin, myoglobin, desmin, cytokeratin, were assessed immunohistochemically. GFAP and S-100 protein appeared at the 6th week of GA in primitive glial cells of the cerebellar anlage, brain stem, rhombencephalon, and developing spinal cord, together with--as first neuronal marker--chromogranin A, then NFP (70 and 200 kDa, and 160 kDa) from the 8th week onward. NSE started in the 11th week and synaptophysin not earlier than the 16th week of GA. Interestingly, the differentiation of the retinal anlage started rather late with NSE positivity beginning from the 16th week and positive reactions to synaptophysin and NFPs only from the 25th and chromogranin A from the 28th week of GA onward.