Intrasplenic grafting of 7,12-dimethylbenz (a) anthracene-treated ovarian piece.

Immediately after a direct application of a chemical carcinogen, 7,12-dimethylbenz (a) anthracene (DMBA), the ovarian piece containing DMBA was implanted into the spleen of Wistar strain rats with or without gonadectomy. Six months after these treatments, an intrasplenic neoplasm was found in four of nine gonadectomized rats and in two of ten rats without castration. The volume of the induced tumor in the former group was 1.85 cm3 in average and that in the latter was 0.25 cm3. Histologic examination indicated that all of the induced tumors were not in the sex cord-stromal category, but adenocarcinomas. No morphological differences between the tumors in the castrated group and those in the noncastrated group could be detected by light microscopy. From the difference in the volume and the incidence of the induced tumors in the two groups, it appears that the hyperstimulation of the pituitary gonadotropins in the castrated rats promoted the tumorigenic process of the induced 'epithelial' ovarian cancer caused by the DMBA application to the grafted ovarian pieces.