[Differentiation in primitive neuroectodermal tumors. Significance of histology and immunohistochemistry for...

Surgical samples collected from 17 patients with "primitive neuroectodermal tumors (PNET)" were retrospectively tested for signs of cellular differentiation, using histological and immunohistochemical procedures. Histological characteristics of astrocytic differentiation were exhibited by 10 tumors. Expression of glial fibrillary acid protein (GFAP) was recorded from tumor cells in 8 cases. Assessment of astrocytic differentiation proved to be difficult with either method. Both of them, therefore, should be used in combination. Histological characteristics of neuronal differentiation were less often observed but were identifiable with relatively high unambiguity. Immunohistochemical detection of neurofilament (NF) protein appeared to depend on the presence of mature neuronal structures. Tests for that purpose were negative in all cases at hand. Its importance to differential diagnosis is believed to be low. Protein S 100 was recordable from tumor cells in 10 and vimentin in 7 cases. While both markers were found not to be specific of a certain direction of differentiation, they added to information on tumor cell maturity. Oligodendroglial structures appeared to be closely linked to occurrence of neuronal differentiation. Oligodendrocytes may possibly play a key role in maturation of neuronal cells.