Olfactory neuroblastoma in a heifer.

A nasal neuroblastoma (esthesioneuroblastoma) extending into the brain in a heifer produced mouth breathing and proptosis. The mass filled much of the left nasal cavity, palatine sinus and maxillary sinus, with turbinate atrophy and deviation of the septum. Caudally the neoplasm extended into the nasopharynx and olfactory bulb. It was a cellular neoplasm composed of small, undifferentiated piriform cells showing infrequent pseudorosettes and immature axonal processes. Mitosis was common is some areas.