Cytology of spontaneous adenomas in the pituitary gland of the rat.

In recent years, the spontaneous appearance of adenomas in the anterior hypophyses of rats has been described by Wolfe, Bryan, and Wright (39), by Oberling and his associates (24), by Saxton (28) and by Saxton and Graham (29). These adenomatous growths have been found almost entirely in the anterior lobes of old rats and their presence is seemingly a manifestation of advancing age. The size. appearance and cellular constituents of these adenomatous lesions is variable, Wolfe, Bryan and Wright (39) having described three types. The first type was characterized by varying amounts of hemorrhage and was classified as a hemorrhagic adenoma. These growths ranged in size from small lesions of 0.4 X 0.5 ram., which could not be recognized grossly, to large swollen tumors involving practically the entire anterior lobe. Histologically they were composed of chromophobes although small numbers of acidophiles were present in some instances. The chromophobe cells in these lesions generally, but not invariably, showed various degrees of hypertrophy, some being of enormous size. The adenomatous acidophiles were invariably enlarged. Capsules were not present about these lesions although the neighboring anterior lobe tissue was often compressed. The second type of lesion was designated as an adenomatous nodule. They were made up of small diffuse masses of enlarged chromophobes or acidophiles and sometimes both. The smallest of these nodules contained only a few cells while the largest measured only 0.4 X 0.6 mm. Hemorrhages were not present and there was no compression of the surrounding tissue. The third type of adenoma described by these authors was large, occupying practically the entire anterior lobe, and was made up entirely of chromophobic cells of varying size. There was no evidence of hemorrhage. In all three types of lesions, there was a marked tendency for the nuclei and nucleoli of the adenomatous cells to be enlarged and often there was hypertrophy of the negative image of the Golgi