Spontaneous ovarian neoplasms of the laboratory rat. Vet Pathol

Abstract. A wide range of spontaneous tumors of the ovary are reported in a group of 5903 aged female Sprague-Dawley rats of the CD and CFY strains examined since 1978 in this laboratory. The most commonly observed tumor was the tubular adenoma. Others recorded were tubular adenocarcinoma, papillary cystadenoma, papillary cystadenocarcinoma, a Sertoli’s cell tumor, benign and malignant granulosa cell tumors, benign thecal cell tumors, and classical mesotheliomas of ovarian origin. A system of classification and nomenclature of the ovarian tumors from this group is advanced. Although the literature abounds with references to experimentally induced ovarian neoplasms in labora-tory rats, there is little information relating to their spontaneous occurrence. One study4 drew on a sample population of only 300 animals, while a second ’ re-ferred to spontaneous tumors, but principally dealt with those of experimental origin, i.e., induced. Significant differences exist between the reproductive cycles of the most studied species (man and dogs) and that of the rat, and thus disparity in incidence, structure and behavior between the species is to be expected with ovarian tumors. The various published classifications of ovarian tumors in many species require the availa-bility of clinical information for their full application. In the rat, data relating to individual endocrine func-tion rarely are available and tumors of the ovary rarely are suspected or diagnosed prior to death. Most of these tumors are found as incidental observations during routine histological screening of tissues. For this reason, any system of tumor classification in the rat must be principally morphological. The proposals in this paper have drawn on the experience of the work of Serov an