Induction of ovarian tumors in mice by X-rays.

The production of ovarian neoplaslns in female mice by x-rays was described in 1936 (7, 10). q]ae tmnors arose about 7 to 10 months following irradiation with single or multiple doses of 200 r to 400 r. These tumors were of 3 histological types: (a) granulosa cell tumors, (b) luteomas, and (c) tubular adenomas. Whether the gland or duct-like structures of some of these adenomas are related to arrhcnoblastomas has not bccn determined. Frequently, different parts of the same induced tunmr had a different appearance. Beginning about 5 months after irradiation hypcrplastic changes were present in the ovaries of most x-rayed mice not bearing tumors. The borderline between neoplasia and hyperplasia was indistinct (3). Brambell and Parkes (17) have carefully described the hyperplastic ovarian changes that follow irradiation but they terminated flleir experiments about 6 months after irradiation, and were apparently unaware of the preneoplastic character of these alterations. During the past decade little attention was given to the induction of ovarian tumors by x-rays and it was questioned whether the bulky masses of ovarian cells, which are formed after irradiation, were truly neoplastic. Traut and Butterworth (19) noted a great similarity between ovarian neoplasms of women and the experimentally induced tumors of mice, and traced the development of granulosa cell tumors of mice to granulosa cells that escaped destruction by x-rays. Geist, Gaines and Pollack (13), the only ones to repeat our experimental work, produced ovarian tumors in 22 of 38 mice by a single exposure to 200 r. They believe that the neoplastic granulosa cells arise from undifferentiated cells of the ovarian parcnchyma.