Pineoblastomas are quite rare in adults. The tumors are often seen invading nearby structures and tracking along the leptomeninges, as was seen in this case. Microscopically, the neoplastic tissue is hypercellular with tumor cells having large hyperchromatic nuclei with one discrete nucleolus and scant eosinophilic cytoplasm.
Mitotic activity varies.
Immunostaining patterns demonstrate scattered positivity for synaptophysin, neuron specific enolase and retinal S-antigen. Immunostaining for glial fibrillary acidic protein is inconsistently positive. This pattern of EM findings was observed in our case. The cell of origin of the pineoblastoma is believed to be an immature, arrested or poorly differentiated pineocyte. During developoment, the normal pineal gland recapitulates the developmental program of the retina.