Introduction: The glial differentiation in pediatric "supratentorial primitive neuroectodermal tumors" (sPNET) is occasionally revealed by immunohistochemistry with GFAP (glial fibrillary acidic protein) as isolated positive cells among undifferentiated cells, indicative of divergent cellular phenotypes. Large malignant glial tumors in sPNETs are extremely rare and challenge the neuropathologist by raising the possibility of glioblastomas with sPNET-like features (GB sPNET). The distinction between them is important because of their different treatment and prognostic.
Case presentation: A large parieto-occipital tumor with minimal ventricular invasion, in an 11-year-old girl, with a five-month clinical history, was proven to be a highly malignant biphasic tumor, consisting in a glioblastoma with giant cells, representing 75% of the tumor, and sPNET nodules, with one larger dominant nodule. The immunohistochemistry confirmed positivity for synaptophysin, neurofilament, neuron-specific enolase and CD56 in the sPNET compartment and for GFAP, CD56 and vimentin in the glioblastoma. In some parts of the tumor, the two components were well delineated from each other as in a "collision" tumor, but in others, the two different tumors were intermingled. It was histologically diagnosed as sPNET with double differentiation (glial and neural) or glioblastoma with sPNET-like features.
Conclusions: These cases are very rare, few reported, especially in the pediatric population, and with high difficulties in histological differential diagnosis, subsequently reflected in the therapeutic decisions.