Ependymoblastoma in a Japanese Black heifer

An 18-month-old, Japanese Black heifer had ananastasia over a two-week period. The heifer was euthanized and necropsied. Grossly, a brown and soft mass was found in the left cerebellar hemisphere, which originated from the fourth ventricle in the pons. Multiple papillary masses were also found on the wall of the fourth ventricle. There was massive dilatation of the cerebral aqueduct, and also in the third and lateral ventricles. Histologically, the neoplastic cells formed numerous ependymoblastic rosettes and perivascular pseudorosettes. In the fourth ventricle, the normal ependymal cells were replaced by papillary proliferation of the neoplastic cells. Ultrastructually, the neoplastic cells had a feature differentiating to the ependymal cell showing a few basal bodies in the cytoplasm and connecting to adjacent cells with junctional complexes. We diagnosed the present case as ependymoblastoma with its origins in the fourth ventricle.