Morphological investigations of mixed pituitary adenomas

Thirteen pituitary adenomas were investigated by light and electron microscopy and in tissue culture. In all adenomas the production of growth hormone and prolactin was proved by endocrine symptoms of the patients and by laboratory tests. Histopathological findings were compared with culture characteristics. In 3 cases the adenoma consisted of three kinds of cell population, in 7 cases of two kinds, and in other 3 cases of one kind. In cases where 3 kinds of cell population were found, beside the granulated cells star-shaped forms without secretion granules could be observed. They probably corresponded to follicular cells. In three cases one single cell population was found. In these cases two different hormones might have been produced by one type of cell. These cells could be considered stem-like cellular elements or differentiated committed cells.