Pineal Parenchymal Tumor of Intermediate Differentiation with Gangliocytic Differentiation

A 49-year-old man presented with an extremely rare case of pineal parenchymal tumor with gangliocytic cells, manifesting as progressive gait disturbance and urinary incontinence lasting for one year. Brain MRI revealed a homogenously enhancing mass, measuring 3.5×2.7 ×1.7 cm, in the pineal body. The mass compressed the deep cerebral vein with superior displacement, which caused mild obstructive hydrocephalus. Histological examination revealed lobular structures consisting of isomorphic small round cells with stippled chromatin and clear cytoplasm, and less cellular areas having large pleomorphic cells and ganglioid cells. Mitotic figures and tumor necrosis were not evident. Immunohistochemically, the neoplastic cells were positive for neuronal markers (neuron-specific enolase, neurofilament, NeuN and synaptophysin), but not for glial fibrillary acidic protein or S-100. Especially, neurofilament showed diffuse interstitial immunoreactivity with accentuation in a few gangliocytic cells and Ki-67 labeling index (2.5%) was low. Therefore, this case was diagnosed as pineal parenchymal tumor of intermediate differentiation with gangliocytic differentiation.