| Summary: | Bronchogenic carcinoma (lung cancer) is a major source of morbidity and mortality in industrialized nations. Although bronchogenic carcinoma is largely a preventable neoplasm, it will undoubtedly remain a major medical concern throughout this century, and considerable effort needs to be directed towards its early detection, establishing effective treatment, and understanding the neoplastic process.
The objective of this study was to develop a practical and reliable model of localized bronchogenic carcinoma in laboratory rodents. This was done by impregnating cotton threads with the potent carcinogen, benzo(a)pyrene (BP). These BP-impregnated threads were then coated with a silicone rubber sheath to control the release of BP from the threads. The prepared threads were sewn around four cartilage rings in the ventral tracheal wall of guinea pigs and hamsters. The animals were sacrificed periodically, and two histopathologists graded the tracheal epithelium adjacent to the thread.
The first experiment consisted of 94 Camm-Hartley guinea pigs: 48 experimental animals with BP-impregnated threads and 46 control animals with non-impregnated threads. The second experiment consisted of 70 Golden Syrian hamsters: 54 experimental and 16 control animals. The data showed that the implantation of the thread in the trachea induced a regenerative hyperplasia of the epithelium, and that the BP initiated carcinogenesis. Squamous metaplasia and progressive intraepithelial neoplasia (IEN) was evident prior to the development of squamous cell carcinoma (CA). In the experimental guinea pigs, only one guinea pig developed an invasive CA at 265 days. In the experimental hamsters, the first CA was seen at 55 days and after 120 days, 65% of the animals showed histopathologic evidence of CA. Most of the hamsters with CA also had spindle cell tumors in the tracheal stroma. The control hamsters and guinea pigs did not develop IEN, and the mature respiratory epithelium was reconstituted.
We conclude that this method produced localized, readily accessible preneoplastic and neoplastic lesion in the trachea of hamsters, and to a lesser extent in guinea pigs. The model should prove useful in the study of tumor ultrastructure, the immunologic response to cancer, and the relationship of diet to cancer. === Medicine, Faculty of === Pathology and Laboratory Medicine, Department of === Graduate
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