Pituitary adenoma with prolactin and growth hormone production in a sheep

A pituitary adenoma was found in a 6-year-old ewe. This tumour was composed mainly of chromophobic cells, but acidophilic cells predominated in a few areas. Prolactin was demonstrated in the cytoplasm of some chromophobic cells by means of the immunoperoxidase technique, and secretory granules ranging in size from 100 to 900 nm in diameter were seen in all chromophobic cells examined. Almost all acidophilic cells were positive for growth hormone (GH), and a few of them were also positive for prolactin (PRL). This tumour resembled a human mixed GH cell-PRL cell adenoma.

Functional morphology of spontaneous hyperplastic and neoplastic lesions in the canine pituitary gland

The pituitary glands of 10 male and 29 female dogs of different breeds had diffuse hyperplasia and hypertrophy of growth hormone or prolactin cells. Immunoreactive adrenocorticotrophin/melanotrophin was in the frequent focal hyperplastic lesions and micro- and macroadenomas of both pars distalis and pars intermedia of old female dogs. Pituitary tumours of other functional cell types were not found. Focal hyperplastic and neoplastic lesions usually were accompanied by spontaneous nodular hyperplasia or adenomas of the adrenal cortex as well as by changes in serum adrenocorticotrophic hormone and cortisol levels.

Hyperinsulinism in dogs with neoplasia of the pancreatic islets. A clinical, pathologic, and ultrastructural study

Neoplasms of the pancreatic islets in 6 of 9 dogs were functionally active and were associated with a syndrome of hyperinsulinism. The serum concentration of immunoreactive insulin in a dog with beta-cell carcinoma was increased compared to normal dogs. Metastases in the liver and lymph nodes remained functionally active and were responsive to tolbutamide following excision of the primary neoplasm. The cells comprising functional islet-cell neoplasms had ultrastructural and histochemical characteristics of beta cells. At the level of ultrastructure the neoplastic cells had definitive evidence of secretory activity and the organelles concerned with protein synthesis were well developed. Secretory granules were numerous and had unique bar-shaped or round internal cores with a wide electron-lucid halo, characteristic of the insulin-secreting cell of the canine pancreas.