Squamous cell carcinoma arising from an epidermoid cyst in the ovary of a rat treated with 7,12-dimethylbenz[a]anthracene.

Primary non-teratomatous ovarian squamous cell carcinomas are very rare. A case of rat ovarian squamous cell carcinoma has been found in which the tumor arose from a squamous element in the ovary. Squamous epithelial aggregates were found in the wall of a cyst and on serial section, the cyst was found to be unaccompanied by any teratomatous components and showed a thin squamous epithelial lining with keratinizing debris. On the basis of these findings, it was suggested that the squamous element was a rat ovarian epidermoid cyst from which a squamous cell carcinoma arose, presumably by a direct carcinogenic effect of 7,12-dimethylbenz[a]anthracene.