Carcinogenesis in canine bistomal heterotopic tracheal grafts

Successful canine lung cancer models have required repeated focal bronchial carcinogen exposure under general anesthesia. To simplify serial studies of the respiratory mucosa during carcinogenesis, bistomal autologous heterotopic tracheal pedicle grafts have been made. These grafts can readily be returned to the original orthotopic site, and this has been shown to be a method with which to study reversibility of mucosal changes. Polycyclic aromatic hydrocarbons were applied topically to the mucosa three times a week for 21 to 22 months in 21 grafts. Implants of Silastic polymer from which carcinogen was released in sustained-release fashion were then left in the grafts for 4 to 6 weeks. Serial cytological and histological examinations showed development of atypical squamous metaplasia in the graft mucosa. Mucosal papillomatosis was noted in 4 of 7 grafts surgically excised 17 to 18 months after completion of carcinogen exposure. The heterotopic bistomal tracheal graft provides a useful method for studying respiratory epithelial carcinogenesis without repeated general anesthesia.