Cytological study on pituitary adenomas in senile untreated beagle bitches.

Pituitaries from 25 senile untreated Beagle bitches aged 7-11 years, have been examined using a specific staining technique. In 10 out of 25 animals (40%), pituitary adenomas were detected. In general, pituitary neoplasms were observed as small nodules (2-3.5 mm in diameter) during gross examination or a incidental findings during the microscopic examination. Histological examination showed that the adenomas observed during gross examination were made up either of ACTH cells or of a combination of ACTH and immature cells; the adenomas which were observed as incidental findings during microscopic examination were made up of ACTH, immature or intermediate zone cells. The possible histogenesis of pituitary adenomas, especially the immature cell adenoma, is discussed.