Abstract
The steady-state native fluorescence spectra of extracts of normal mucosa as well as of different stages of oral lesion of the 7,12-dimethylbenz (a) anthracene (DMBA)-induced hamster cheek pouch carcinogenesis model have been measured and analysed at 405 nm excitation. The emission spectra were scanned from 430 to 700 nm to characterize the native fluorescence of endogenous porphyrin and other fluorophores under various tissue transformation conditions, such as hyperplasia, papilloma, early invasive carcinoma and well-differentiated squamous cell carcinoma. Two ratio parameters, R1 = (I530/I620) and R2 = (I530/I630), are introduced to quantify the diagnostic potentiality. The ratio values were found to decrease as the stage of the cancer increases. The suggested critical values for both R1 and R2 for normal mucosa is above three, and the suggested critical value for tissues with lesion is less than three. It was also found that the values for R1 and R2 for well-differentiated squamous cell carcinoma is less than one. The ratio parameter R2 is selected for discrimination between normal mucosa and oral lesions, as the difference in the R2 value between normal and DMBA-treated tissue is higher than that for R1.
Highlights
The epidermoid carcinoma was induced by topical application using a brush of a 0.5% solution of DMBA in liquid paraffin for 16 weeks
During 10-12 weeks of DMBA application, mucosa were found with numerous modular growths and histologically showed early invasive carcinoma with numerous fully formed cell nests and features of well-differentiated squamous cell carcinoma
After 14-16 weeks, the size of these tumour growths was larger; the histology was characteristic of well-differentiated squamous cell carcinoma, demonstrating marked invasion by nests of the tissue underlying the epithelium
Summary
The experimental epidermoid carcinoma of the hamster buccal cheek pouch is a widely studied oral mucosa membrane tumour model (Sally, 1954; Morris, 1961; Shklar et al, 1979). After four weeks of DMBA application, the mucosa were rough, reddish in colour, thickened and vascularized. They showed hyperplastic changes of the lining squamous cells with infiltration of mononuclear cells. During 10-12 weeks of DMBA application, mucosa were found with numerous modular growths and histologically showed early invasive carcinoma with numerous fully formed cell nests and features of well-differentiated squamous cell carcinoma. After 14-16 weeks, the size of these tumour growths was larger; the histology was characteristic of well-differentiated squamous cell carcinoma, demonstrating marked invasion by nests of the tissue underlying the epithelium. The entire mass consisted of infiltrating squamous cells as a network of loosely arranged connective tissue fibres with pronounced atypical mitotic activity
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