Reactive Splenomegaly and Variation of Lymphoid-plasma Cell Population Associated with a Mouse Pituitary Thyrotropic Tumor.

A transplantable thyrotropic pituitary tumor, subline L24a, which grew after 13 months of dormancy in an intact mouse was associated in its early passage with a variety of lymphoid tumors. On subsequent passage, slow growth over a 6to 12month period was regularly accompanied by striking splenomegaly without lymphoid or thymic neoplasia. The enlargement was due to a great increase in cells of the lymphoid series in the red pulp without loss of splenic architecture. In thyroidectomized mice plasma cells with many Russell bodies were especially numerous, and these cells were found hi hypertrophied lymphoid follicles within other organs. It is suggested that the splenomegaly and, hi earlier passage the lymphoid tumors, may represent an exaggerated antibody response to a tumor's having unusual or abnormal hormonal activity. The transplanted pituitary tumors, in turn, showed severe hemorrhagic degeneration with peripheral small lymphocyte stasis in the lymphatics.