A series of esophageal lesions, mild, moderate and severe dysplasia, carcinoma in situ (CIS), early and advanced squamous cell carcinoma were induced in rats with N-methyl-N-amylnitrosamine (MAN). To evaluate the biological nature of each lesion, the ploidy level was estimated by microspectrophotometrical measurement of cell nuclear DNA content. DNA distribution patterns were classified into types I, II, III and IV, according to the degree of dispersion and the peak modal value on the DNA histogram. The incidences of type III of high ploidy in early cancer, CIS and severe dysplasia were 3 11 (27.3%), 5 13 (33.3%) and 4 16 (25%), respectively. On the other hand, in moderate and mild dysplasia, 15 16 (93.8%) and 20 21 (95.2%) were low ploidy (types I and II), respectively. The mean DNA content of advanced and early cancer, CIS and severe dysplasia were 3.88c, 3.34c, 3.24c and 3.13c, respectively, while those of moderate and mild dysplasia were near diploid, showing 2.67c and 2.51c, respectively. These findings indicate that the biological nature of severe dysplasia may be considered as serious a lesion as cancer, in terms of DNA analysis. Cytophotometric DNA analysis aids the evaluation of various degrees of dysplasia and carcinoma of the esophagus.
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