DNA content in carcinoma of the rectum and rectosigmoid.

Using single cell cytometry the pattern of DNA content in preoperative samples from 131 carcinomas of the rectum and rectosigmoid has been studied. For comparison, 21 carcinomas of the colon, 44 colorectal polyps and mucosa adjacent to the tumours were also included. The biopsies were classified into near diploid (ND), near diploid with aneuploid cells (ND-anc) and aneuploid (AN). A more specific subclassification of aneuploid samples was not consistent because of a commonly occurring multiclonality, where different clones dominated different parts of the tumours. Fifteen of all 130 representatively sampled rectal carcinomas were ND; however, all the ND scores were based on a single sample. Among 31 multiply-sampled carcinomas none registered as ND in all samples. There were no principal differences in patterns of DNA profiles between rectal and colon carcinomas. Five samples from the pericancerous mucosa and samples from 4 adenomas showed non-ND patterns, which may be a premalignant sign. The main conclusions of these results are that rectal carcinomas, even if they contain a substantial ND cell population, to a very great extent contains cells with an abnormal DNA content. The carcinomas can be classified according to their pre-operatively estimated DNA content. The clinical relevance of this will be judged when the patients have been followed for longer time periods.