Morphology and histogenesis of anal region and clitoral gland tumors induced in mice by 1,2-dimethylhydrazine.

Ninety-seven tumors induced in the anal region in female CBA and BALB/c mice by 1,2-dimethylhydrazine were examined histologically. Tumors originated mainly from the following sources: epidermis (papillomas and basal cell neoplasms), pilosebaceous complexes of the anal region (keratoacanthomas, cystic squamous cell tumors, and adenomas of the perianal sebaceous glands), and clitoral (preputial) glands (adenomas and adenoacanthomas). A subcutaneous location and late ulceration were characteristics of many tumors originating from the pilosebaceous complexes and clitoral glads. From 31 to 43% of all anal tumors were of sebaceous gland (perianal or clitoral) origin. Cystic squamous cell tumors were morphologically similar to type II keratoacanthomas of rodents. Squamous cell tumors of any origin finally became squamous carcinomas.