[An ultrastructural immunocytochemical study of secretory granules of an adenohypophyseal tumor].

The unlabeled antibody peroxidase-antiperoxidase complex technique was used to stain for electron microscopy the secretory granules of a pituitary tumor that had been surgically removed from a woman with high serum prolactin levels. Granules were stained using anti-human prolactin serum. The diameter of the secretory granules was smaller than that measured for the granules of prolactin producing cells in normal human pituitary glands. A shortened storage phase would explain the diameter reduction.