Ovarian neuroglial choristoma in a dog.

Neuroglial choristomas are rare in humans and animals. During a routine medical examination, an ovarian mass was found in a 5-y-old female mixed-breed dog. Histologically, the ovarian mass was well-defined, expansile, and composed of large polygonal cells resembling well-differentiated neurons and scattered smaller cells resembling glial cells. Immunohistochemically, the neuron-like cells were positive for neuronal nuclei; the smaller cells were positive for glial fibrillar acidic protein, oligodendrocyte transcription factor 2, and ionized calcium-binding adaptor protein-1. Ovarian neuroglial choristoma was diagnosed.