A light and electron microscopical study of pituitary adenomas.

Authors studied ten cases of human pituitary adenomas, using light and electron microscopical techniques. Based on morphological features correlated with endocrine symptomatology, seven adenomas proved to be functional and three were nonfunctional. The seven secretory adenomas were classified as follows : somatotropic adenomas with densely granulated cells (1 case); prolactinomas with sparsely granulated cells (3 cases); and mixed somatotroph cell - prolactin cell adenomas (3 cases). The nonfunctional tumors belonged to the undifferentiated cell adenoma type. The cells of the densely granulated adenoma resembled the normal cell from which they derived. In the sparsely granulated tumors the secretory granules were smaller and more nonspecific than those of the normal pituitary cells. The cells of the undifferentiated adenomas had sparse organelles and often showed oncocytic transformation. The ultrastructural characteristics of the adenomas are discussed in relation with the type of hormonal secretion and proliferative propension.