Pineoblastoma with neuronal differentiation--immunohistochemical and immunocytochemical studies.

Immunohistochemical and immunocytochemical studies were performed on a specimen obtained at operation from a 4 year-old female with intracranially spread pineal tumor in the right temporal lobe. Microscopically, it was a highly cellular tumor, and the cells contained chromatin-rich round or oval nuclei and scanty cytoplasms. There were numerous mitotic figures. Rosettes were not detected. Both immunohistochemical staining of paraffin-embedded sections and immunocytochemical staining of short-term cultured cells disclosed a subgroups of cell positive for NSE and 68K-NF (neurofilament). No cells were positive for GFAP, S-100 protein or HCG. From these findings, the tumor was thought to be pineoblastoma, which is an undifferentiated tumor that rarely shows divergent differentiating potential. This is the first report of pineoblastoma with the differentiation only toward the neuronal line confirmed by the analysis of immunohistochemistry and immunocytochemistry.