Flow cytometry has been used to study the incidence of aneuploidy in a series of 55 colorectal adenomas (29 tubular adenomas, 22 tubulovillous adenomas, and 4 villous adenomas). For comparison, 5 nonadenomatous polyps, 4 normal mucosa samples from colectomy specimens and 16 colorectal cancers were measured. Fifteen (27%) adenomas were aneuploid, 33 (63%) were diploid, and 7 (11%) were peridiploid. The aneuploidy incidence increased with the size of the adenomas (<1 cm, 0%; 1 to 2 cm, 30%; >2 cm, 50% aneuploid cases, respectively) but was less dependent on the histological type or degree of dysplasia. However, the degree of aneuploidy [mean DNA index of aneuploid stem lines] was significantly higher in tubulovillous adenomas [1.26 ± 0.33 (SD)] than in tubular adenomas [1.09 ± 0.04] and only slightly lower than in carcinomas [1.59 ± 0.26].

The progressive increase in ploidy abnormality with size and histological type strongly supports the evidence for the adenomacarcinoma sequence in the development of colorectal cancer.

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