4-Nitroquinoline-N-Oxide의 백서 구개도포에 의한 이차적 설암유발에 관한 실험적 연구

EXPERIMENTAL STUDY OF LINGUAL CARCINOMA SECONDARILY INDUCED BY LOCAL APPLICATION OF 4-NITROQUINOLINE-N-OXIDE ON RAT PALATE

Lingual carcinoma are difficult to induce than other part experimentally, thereby preventing studies of pathogenesis, biology and histology of the tumor. The present study was to describe the gross and histopathologic changes of tongue carcinoma secondarily induced by local application of 4-Nitroquinoline-N-oxide(4NQO) on rat palate. 55 albino rats, Sprague-Dawley strain were used for experimental animal, propane-1,2-diol for control group(15), 0.5% 4NQO solution diluted in propane-1,2-diol for experimental group(40) were painted on the palate 3times weekly for 30 weeks with No.2 brush. The animals were sacrificed 2 every 4 other weeks for control group, 2 every other weeks for experimental groups. The obtained results were as follows; 1. In the control group, no changes were noted during experimental periods grossly and showed irregular surface due to well-developed filiform papilla histologically as normal tongue. 2. In the experimental group, focal loss of papilla, mild acanthosis and infiltration of chronic inflammatory cells in 10 weeks, mild dysplasia only in 16 weeks, after that, no specific change and followed by well-differentiated squamous cell carcinoma from 32 weeks observed experimentally. 3. Tongue carcinoma induced by indirect contact with carcinogen were induced in 8 weeks later than palatal carcinoma by direct application of carcinogen, and abruptly appeared in 32 weeks of experimental period without gradual changes grossly and histopathologically. 4. Grossly, induced tongue carcinoma showed ulcerative or/and exophytic patterns around the crest on the dorsum of tongue, and histologically, it was well-differentiated squamous cell carcinoma that shows loss of papilla, hyperkeratosis, infiltration of chronic inflammatory cells and keratin pearl formation with infiltrative growth into underlying connective tissue and muscle layer. Transition focus between mucosal layer and tumor lesion, and no tumor emboli in blood vessel were observed.