Clinicopathologic features of intracranial central neurocytomas in 2 dogs.

BACKGROUND: In humans, central neurocytomas are rare and typically benign intracranial tumors found within the lateral ventricles, although extraventricular variants have been reported. Intracranial central neurocytomas have not been previously recognized in domestic animals. OBJECTIVES: To describe the clinicopathologic features of canine intracranial central neurocytomas. ANIMALS: Two dogs with spontaneous intracranial and intraventricular neoplasms. RESULTS: Both dogs experienced seizures, rapid neurological deterioration, and death from tumor-associated complications within 5 days of the onset of clinical signs, and had neoplastic masses within the lateral ventricles. A brain MRI was performed in 1 dog, which revealed a T1-isointense, heterogeneously T2 and FLAIR hyperintense, and markedly and heterogeneously contrast-enhancing mass lesions within both lateral ventricles. Histologically, the neoplasms resembled oligodendrogliomas. The diagnosis of central neurocytoma was supported by documenting expression of multiple neuronal markers, including neuron-specific enolase, synaptophysin, neural-cell adhesion molecule, and neuronal nuclear antigen within the tumors, and ultrastructural evidence of neuronal differentiation of neoplastic cells. CONCLUSIONS AND CLINICAL IMPORTANCE: Central neurocytoma should be a differential diagnosis for dogs with intraventricular brain masses. Morphologic differentiation of central neurocytoma from other intraventricular neoplasms, such as ependymoma or oligdendroglioma, can be difficult, and definitive diagnosis often requires immunohistochemical or ultrastructural confirmation of the neural origin of the neoplasm.

Extraventricular neurocytoma of the spinal cord in a dog.

Central neurocytoma is a rare, prognostically favorable neuronal tumor of the human central nervous system, typically located intraventricularly near the foramen of Monro. Extraventricular cerebral neurocytomas and spinal tumors have also been reported. To date, however, neurocytomas have not been documented in domestic animal species. In this report, we describe a spinal cord tumor in a dog. The microscopic examination revealed tumor cells forming loosely packed clusters in some areas and palisades in other areas. In addition, they showed fine fibrillary neuropil-like areas of different sizes, sometimes resembling the "rosettes" of pineocytomas, as well as ependymoma-like perivascular pseudorosettes. The tumor cells had scant eosinophilic cytoplasm, with perinuclear halos, closely resembling the appearance of oligodendroglioma. Immunohistochemical staining showed expression of synaptophysin and neuron-specific enolase by tumor cells and pronounced in fibrillary areas. On the basis of histomorphology and immunohistochemical reactivity, the present tumor was diagnosed as extraventricular neurocytoma.