Histologic characterization of rat ovarian carcinoma induced by intraovarian insertion of a 7,12-dimethylbenz[a]anthracene-coated suture common epithelial tumors of the ovary in rats?

BACKGROUND. The surface epithelium of the human ovary simulates the mullerian form in tumor formation. In experimental animals, however, such a phenomenon has not previously been observed. METHODS. A chemical carcinogen, 7,12-dimethylbenz[a]anthracen (DMBA), was heated, and the central portion of a 3-0 silk suture was immersed in the melted carcinogen. After vaginal cytology, the DMBA-coated silk was inserted into the ovaries of 40 Wistar strain rats age 7 weeks. The animals were sacrificed when a tumor mass became large enough to extend the abdominal wall. The experimental period lasted for 60 weeks. The tumor histology was compared with that in human counterparts and the mullerian derivatives in rats. RESULTS. In 19 rats, including 4 animals with cornified vaginal smears at the time of DMBA treatment, an ovarian carcinoma developed within 36 weeks. In 17 epithelial tumors, the neoplastic cells proliferated to form papillary or glandular structures, and the lining epithelium consisted of flattened or cuboidal cells and columnar cells, often with pseudostratified nuclei. Adenocarcinoma components transformed into squamous cells in two cases. The remaining two neoplasms were pure mesenchymal tumors with histology of a fibrosarcomatous tumor, and one of them contained heterologous malignant osteoid components. In the remaining 21 rats, including 5 with cornified smears, no tumors developed during the experimental period. CONCLUSIONS. The histologies of DMBA-induced rat ovarian carcinoma simulated the epithelia of rat ovarian surface, fallopian tube, endometrium, and uterine cervix. The results of this study suggest that the surface epithelium of rat ovary also simulates the mullerian form in tumor formation.