Histopathologic studies of DMBA-induced mouse submandibular-gland tumors with or without cryoprobe treatment

Histopathologic observations of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced tumors in the mouse submandibular glands are reported using cryoprobe treatment. The experimental animals were divided into 2 groups; one received a carcinogen injection into the normal submandibular gland, and the other was injected with DMBA on the 14th day following cryosurgery of the gland using a -60 degrees C cryoprobe. Pathologic findings were classified as premalignant lesions or squamous-cell carcinomas with varying degrees of keratinization, fibrosarcoma and mixed carcinoma. There was also one case each of malignant pleomorphic adenoma and cystic adenoma. Tumor incidence was nearly the same in the 2 groups. Most of the carcinomas and sarcomas in the submandibular gland were induced during the 12th and 17th weeks. DMBA application during the proliferating stage which followed the cryosurgery did not enhance epithelial-tumor induction. During submandibular gland carcinogenesis, alterations in the granular convoluted tubule cells suggests they were the initial target cells undergoing malignant transformation. Squamous-cell carcinomas with varying degrees of keratinization were induced following squamous metaplasia in duct-like structures or multicystic lesions.