Atypia and Surface Structure of Superficial Neoplasms of the Colon Less Than 10 mm in Diameter

Histological specimens of 30 distinct adenomas and 30 distinct carcinomas were studied by image analysis to quantify nuclear size and shape. These data were used to derive a discriminant equation, which permitted the lesions to be classified into two groups based on nuclear atypia. Next, 50 superficial type tumors of the colon (34 IIa lesions, 9 IIc + IIa lesions, and 7 IIc lesions) <10 mm in longest diameter were similarly analyzed. These lesions were classified into a high atypia index group (HAI group, 14 lesions) and a low atypia index group (LAI group, 36 lesions) by the above discriminatory equation. Differences between these two groups in surface structure, marginal zone properties, and macroscopic type, assessed using a dissecting microscope, were studied. A hyperplastic shape of the tubular orifice was seen at the marginal zone in 10 lesions (27.7%) in the LAI group and 11 lesions (78.5%) in the HAI group. This difference was significant. Surface structure and macroscopic type were not correlated with the degree of atypia. The tubular density in lesions showing a hyperplastic pitted pattern at their border was 77.40, significantly higher than that for lesions without such a pattern (73.12). The contribution of various variables to surface structure, marginal zone properties, and macroscopic type was studied by discriminant analysis. A high correlation was found between marginal zone properties and tubular density. Since lesions with high nuclear atypia tend to have high tubular density, marginal zone properties were secondarily correlated with the level of nuclear atypia. Observation of the marginal zone properties of lesions was thus suggested to be helpful in the diagnosis of lesions with severe atypia.