Neoplasms in the Adenohypophysis of Dogs: A Clinical and Pathologic Study

Twenty-six neoplasms of the adenohypophysis were classified either as chromophobe adenomas (20 dogs) or adenomas of the pars intermedia (6 dogs). In 62% of the dogs the neoplasms were functionally active (14 chromophobe adenomas, 2 adenomas of the pars intermedia) and associated with a syndrome of hyperadrenocorticism (Cushing's-like disease). The adrenal cortical hypertrophy and hyperplasia, muscular weakness and wasting, leukocytosis with a neutrophilia, eosinopenia and lymphopenia, deposition of fat in the liver, increased serum corticosteroid, and increased urinary 17-hydroxycorticosteroids all suggested the neoplasms were producing ACTH. Mineralization of the lungs and other tissues was consistently present in dogs with functional neoplasms. Adenomas of the pars intermedia appeared to arise from the lining epithelium of the residual hypophysial lumen covering the infundibular process. They were sharply demarcated from the compressed pars distalis.