The Cytology of a Human Pituitary Tumor: An Electron Microscopic Study

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Abstract
A human chromo- phobe pituitary tumor was studied with an electron microscope. The tumor consisted of 4 types of cells which were termed granulated, nongranulated, unidentified, and dense cell types. The granulated cell type was characterized by the presence of various-sized secretory granules varying in diameter from 100 m[mu] to 550 m[mu]. The nongranulated cell lacked secretory granules. The unidentified cell had large, electron-dense granules up to 3 [mu] in diameter. The dense cell type was characterized by a much denser cytoplasm than the other cell types possessed. The rough endoplasmic reticulum was in the form of tubules or vesicles. The vesiculated form was predominant in the nongranulated cells and it is thought that this cell type is in a less active stage of secretion than is the granulated cell type. Mitochondria, lipid droplets, and lysosome-like bodies were present in all of the cell types. Fibrous bodies, consisting of fibers approximately 100 A in diameter, were found in the granulated, nongranulated, and dense cell types. The fibers were arranged in a compact whorl-like structure in some cells, whereas in others they were lying loosely In the cytoplasm. The Golgi complex was greatly hypertrophied, and forming secretory granules were found within the Golgi saccules. Centrioles, approximately 240 m[mu] in diameter and 600 m[mu] in length, were described in the tumor cells. These were associated with the Golgi complex and forming fibrous bodies of the tumor cells.