NEOPLASTIC DISEASES OCCURRING AMONG MICE SUBJECTED TO GENERAL IRRADIATION WITH X-RAYS 1 n. OVARIAN TUMORS AND ASSOCIATED LESIONS J. FURTH AND J. S. BUTTERWORTH (From the Department of Pathology, Cornell University Medical College, New York) Mice were subjected to single or repeated large doses of x-rays, 200 to 450 r, as described in the preceding paper (p. 54). Irradiation increased the incidence of myelosis 8 times, of lymphomatosis from 2 to 7 times, while ovarian tumors were approximately 15 times more frequent among the irradi­ ated mice than among their unirradiated siblings (1). The present communication describes the morphological characteristics of the ovarian tumors found among both x-rayed mice and controls and some associated changes. An attempt is made to correlate the histologic characters of the ovarian tumors with hormonal activity, and with the presence or absence of breast tumors. The material is in some respects incomplete. The discovery of the tumors was accidental, and the majority of the animals were discarded without pre­ serving tissues of the endocrine organs. Indeed, the possibility that the ovarian tumors were part of an endocrine disturbance caused by exposure of the entire body to massive doses of x-rays was not recognized until the study was almost completed. We have encountered many findings that are difficult to interpret, but it seemed desirable to present our observations, leaving the solution of these problems to future investigations. The literature abounds in descriptions of the changes which immediately follow exposure to x-rays but nothing is known of the late effects of irradiation on endocrine organs such as the adrenals and hypophysis. It will be the purpose of future investigations to fill this gap in our knowledge. LITERATURE Effect of X-rays on the Ovary: The histologic changes in ovaries exposed to sterilizing doses of x-rays have been fully described in a series of articles by Brambell, Parkes and Fielding (2-7). Reference to the earlier literature may be found in their communications and in the reviews by Regaud and Lacassagne (8), Allen (9), and Zondek (10). Brambell, Parkes and Fielding (2) found that in mice exposed to steriliz­ ing doses of x-rays at weaning time (three weeks old), all the oocytes degen­ erated completely. The cells of the membrana granulosa and the theca in­ terna subsequently underwent a similar change. In some cases the follicles 1 This investigation has been supported by a grant from the Lady Tata Memorial Trust and by a Fund for the Study of Leukemia. 66 NEOPLASTIc DISEASES AMONG MICE SUBJECTED TO X-RAYS 67 did not degenerate, but grew and formed corpora lutea atretica. These per­ sisted but had no effect on the vaginal cycle. Proliferating cords of cells of germinal epithelium penetrated into the medullary region. They formed the major part of the irradiated gonad and were probably the chief source of estrin. A second proliferation of cords from the germinal epithelium oc­ curred, producing anovular follicles. These cords were shown to have no influence on the estrous cycle. Irradiation of non-parous adult mice produced similar changes, but no post-irradiation proliferation from the germinal epithelium was observed (4). The elements already forming the cortex at the time of irradiation persisted. The sterilized ovary consisted of follicles and interfollicular tissue originally derived from the embryonic germinal epithelium. Brambell and his associates believe that these elements produce estrin in the normal ovary and continue to do so without interruption after irradiation. Anovular follicles were formed from the smaller follicles by degeneration of the oocytes and growth of the membrana granulosa cells. These were identical in every respect with the cords of the second proliferation in the animals x-rayed before puberty. The latter, however, developed directly from the germinal epithelium after the follicles had disappeared, and contained no oocytes. The degenerative changes in the corpus luteum of mice irradiated during pregnancy (3) or lactation proceeded more slowly than in normal ovaries and old corpora lutea became in most instances permanent components of ovaries sterilized by x-rays. The salient observations of these investigators have been amply confirmed (9, 10). X-rays when applied to the ovary in amounts sufficient to destroy all ova do not bring about cessation of estrin production, as evidenced by persistence of the estrus cycle. The smallest dose of x-rays that brings about sterilization of the ovary is 200 r in man and 54 r in mice (Schugt, 11). The cycle is present in the mouse even after irradiation with 400 r (10). The amount of estrin excreted in the urine of guinea-pigs with irradiated ovaries is, however, less than normal and the cycles are irregular, with prolonged pe­ riods of estrus, and several months after irradiation the cycle may be alto­ gether absent. Development of mammary glands occurs (Schmidt, 12). Ovarian Tumors in Mice: Primary tumors of the ovary in mice are un­ common. Only two cases have been reported since the elaboration of a clas­ sification of ovarian tumors based upon endocrine function. Schiller (13) irradiated mice with 180 r and subsequently injected them two or three times weekly with hormones of the anterior lobe of the hypophysis. In one of these mice he found, several months after irradiation, bilateral ovarian tumors which he believed were the result of the stimulating effect of hypophyseal hormones on the granulosa cells of the ovary. Apparently he did not investigate the possibility that irradiation alone may be sufficient to produce such growth. While the present paper was in preparation, Gardner, Strong and Smith (14) described a chromophobe adenoma of the hypophysis, granulosa-cell tumors of both ovaries, and adenocarcinomata of the breast in an unirradiated mouse twenty-three months old. ]obling (15) reported the first ovarian tumor in a mouse, which had a sar­ coma of the chest wall and papillary cystadenomata of both ovaries. Later 68 J. FURTH AND J. S. BUTTERWORTH Jobling (16) described a second case in which the left ovary alone was en­ larged. Microscopically there were in this growth many cysts lined by high columnar epithelium without cilia and separated by tubules. Among the tubules there were smooth muscle fibers with many mitotic figures. The more solid parts had the appearance of a leiomyoma. Tyzzer( 17) reported four cases of primary solid papillary cystadenomata of the ovary, of which two were bilateral. These tumors all occurred in mice over twenty-four months of age. They were essentially solid, with con­ spicuous papillary ingrowths, and showed only a slight tendency to form cysts. Tyzzer says that the tumor cells resembled those of the peritoneal mesothelium. Haaland (18) reported two ovarian tumors occurring among 288 mice. One of these was possibly a metastatic adenocarcinoma, the other a solid folliculoma similar to that of our mouse Rr 288 (see p. 74). Slye, Holmes and Wells (19) described 44 cases of primary ovarian tu­ mors occurring among 22,000 mice, an incidence of 0.2 per cent. Simple cysts of the ovary were also encountered but were not included with the tumors. Thirty-eight of the 44 cases were designated as benign solid papillary adeno­ mata and in one-half the tumors were bilateral. One tumor was a solid tera­ toma and one a papillary cystadenoma. The remaining 4 tumors were re­ garded as primary malignant tumors of the ovary. Of the 40 mice with benign ovarian tumors, 14 had one or more tumors of the mammary gland and 3 had adenoma of the lung. The tumors varied from 3 to 10 mm. in diameter', were white and firm, and often showed a lobulated surface. Microscopically they were composed mainly of two types of cells in varying proportions; low cuboidal epithelial cells and spindle-shaped cells like those of the ovarian stroma. The cuboidal cells formed tubules, solid plugs, or alveolar masses. Blood vessels were scanty and mitoses were rarely seen. About the tumor there was in most cases compressed ovarian tissue in which ova and follicles were rarely present. The authors believed that histogenetically the benign tumors were similar growths. Apparently the cells composing the tumors grew under great pressure, which did not allow the same degree of differentia­ tion in all cases. The four tumors that were considered to be primary malig­ nant growths of the ovary were unilateral, and in two metastases were found. Three cases were associated with primary carcinomas of the breast and the fourth case with papillary adenoma of the lung. Mitotic figures were seen in all of these cases. The authors believe that the tumors of the ovary, testicle, and adrenal which they have studied "represent reversions to the primitive embryonal tissues of the urogenital anlage, and are probably best designated by Adami's term, mesothelioma." Figure 1 of Slye, Holmes and Wells, designated as solid tubular adenoma, is like our tubular adenomata with abundant spindle-shaped stroma cells. Their Figs. 9 and 10, designated as malignant epithelial tumors of the ovary, appear to resemble granulosa-cell growths, and the latter may be taken to illustrate solid granulosa-ceIl tumors. Both of these tumors were associated with carcinoma of the breast. A fibrosarcoma of the ovary of a mouse was described by Heidenhain (20). NEOPLASTIC DISEASES AMONG MICE SUBJECTED TO X-RAYS 69 MATERIAL AND METHODS The material studied was obtained from 68 mice with ovarian tumors, of which 57 had been irradiated. Most of these mice belonged to the series described in the preceding communication (1). The rest were found in the course of more recent observations. Irradiated mice with no ovarian tumors were studied for the purpose of investigating the changes that precede the development of ovarian tumors.