DNA ploidy of 64 colorectal adenomas and 49 adenocarcinomas, examined endoscopically, was studied by flow cytometry. We found DNA aneuploidy in none of the 105 normal mucosa samples (O%), in 20 adenomas (31%), and in 36 adenocarcinomas (74%). DNA ploidy of adenomas correlated with size ( P = 0.02) and degree of dysplasia ( P < 0.01) but not with histologic type. Adenomas had a 45% incidence of DNA aneuploid stem lines in the DNA index range of 0.80-1.20, compared with 8% in the case of adenocarcinomas. The distribution of the DNA index values of adenocarcinomas was approximately normal, with a mean value 1.63 f 0.28. The mean DNA index for the three cases of "carcinoma in adenoma" with invasion of the stalk of the adenoma was 1.52 f 0.18. These results, using DNA flow cytometry, provide evidence for the progression of colorectal adenoma to adenocarcinoma. The classification of adenomas according to DNA ploidy may be information of considerable practical value to the clinician in predicting risk of further adenomas andlor risk of cancer.
Key terms: DNA ploidy, DNA index, prognosis Histopathologic, clinical, and epidemiologic data strongly indicate that the majority of cases of colorectal carcinomas develop from pre-existing adenomas (12). The sequence from adenoma to adenocarcinoma has been described as a multistep process (10). Initially, in adenoma-prone subjects, one or more environmental agent induces the appearance of small adenomas. Further factors, which involve still largely unknown mechanisms, cause the development of the adenoma and its progression to adenocarcinoma.
In recent years it has become accepted policy to remove all polyps visible during endoscopy. Polyps, however, tend to reappear, and in some cases a colorectal cancer may develop. The follow-up surveillance of patients after the removal of a colorectal adenoma represents a n important clinical and economical problem; yet no clear guidelines have been established (13,14,23). Classical histopathologic criteria do not appear to be adequate. Recently, DNA aneuploidy, i.e., abnormal flow cytometric DNA content, was shown to be of prognostic value for colorectal adenocarcinomas (1,4,5,9,15,25,26). These findings suggest that DNA aneuploidy may also be relevant to colorectal adenomas, to predict the risk of recurrences andlor the risk of malignant transformation and thereby contribute to the identification of high-risk subgroups of patients.