Electron microscopic studies of human pituitary tumors. I. chromophobic adenomas

Ten cases of chromophobic adenoma have been studied by electron microscopy; seven were associated with hypopituitarism and three with acromegaly. Comparison of the tumors revealed that morphological variations in parenchymal cell types were slight, and, based on characteristics of the secretory granules, a single cell type was predominant and common to both varieties of the tumor. The predominant cell type contained varying amounts of secretory granules that measured 80–200 mμ or more in diameter, and had an electronopaque core and perigranular halo. Though the features of these secretory granules were most like those in “normal” adult basophils this classification is considered doubtful. The core material of the secretory granules was homogeneously electron-opaque in some granules and particulate in others. In addition to electron-opaque core material many secretory granules contained aggregates of clear vesicles. Some granules did not contain clear vesicles but were closely associated with numerous cytoplasmic vesicles. Lysosomes were abundant and a consistent feature of the tumor cells. The present observations indicate that cell features are significantly altered in the cells of both varieties of chromophobic adenoma so that ultrastructural criteria used to identify cell types in “normal” pituitary glands are not applicable to the tumor cells. Chromophobic adenomas associated with acromegaly varied more with respect to the features of the predominant cell type than did chromophobic adenomas associated with hypopituitarism. Cell features varied between cells with electronlucent cytoplasmic matrix and scant development of organelles to others with more electron-opaque cytoplasmic matrix and more complex development of organelles. Common to both varieties of tumor were marked variations in the number and structure of mitochondria from cell to cell; occasionally mitochondria filled the cytoplasm.