A transplantable functional ovarian tumor occurring spontaneously in a rat.

tional ovarian tumors in laboratory rodents, both by irradiation and by intrasplenic transplants, has been extensively studied, there are fewrecords of spontaneous functional tumors in these animals. Spontaneous ovarian tumors of any variety are uncommon in rats. Bullock and co-workers (2, 4) found only six ovarian tumors in 14,038 female rats observed. We have been unable to find any report in the literature of a spontaneous functional ovarian tumor in the rat. In the mouse, spontaneous ovarian tumors are also unusual. Slye and co-workers (8) observed only 44 ovarian tumors in 22,000 mice. Although Cloudman (3) referred to solid, spontaneous ovari an tumors, seen in the mice at Jackson Memorial laboratory, as granulosa-cell tumors, Woolley, who is at the same laboratory, stated that none of these tumors showed evidence of function.1 We have been able to find only two reports (Gardner et al. [6] and Strong et al. [9]) of spontaneous func tional ovarian tumors occurring in mice. It is the purpose of this paper to report a spon taneous functional ovarian tumor in the rat. This tumor displayed a high degree of endocrine ac tivity and has grown readily on serial passage.