Abstract
The pituitary gland was examined from 623 immature baboons (Papio cynocephalus and Papio anubis). Findings included microscopic cysts in the pars distalis (132), pars intermedia (two) and pars nervosa (one). In 641 necropsies five cases of unilateral thyroid glands were noted. Microscopic thyroid lesions included ectopic thymus (328), minor lymphocytic infiltrates (14) and cysts (two). Parathyroid lesions consisted of ectopic thymus (73) and cysts (24). Dilated capillaries in the islets of Langerhans was the only microscopic change seen in the endocrine pancreas. All lesions generally occurred in both untreated control and treated baboons at similar incidences. They were considered to be naturally occurring, a part of the “background” pathology of these endocrine glands in immature baboons.