Evaluation of apoptosis as a factor affecting the growth of non-polypoid colorectal adenomas

Some colorectal adenomas show non-polypoid features endoscopically, e.g. nodule-aggregation or lateral spreading. To understand the developmental mechanism of non-polypoid adenomas better, we evaluated apoptosis indices in the upper and lower parts of 26 colorectal adenomas of non-polypoid appearance using TUNEL or single-stranded DNA (ssDNA) immunohistochemical staining. Regression analysis showed an extremely strong positive correlation between the apoptosis index (AI) values generated using each method. The AI of the lower section of lesion (4.54 +/- 1.86) was significantly higher than that of the upper part (1.21 +/- 1.47). In conclusion, ssDNA immunostaining is as useful as the TUNEL method in the evaluation of apoptosis in colorectal adenomas. It seems that vertical growth in non-polypoid adenomas is inhibited by apoptosis allowing horizontal growth to dominate and resulting in the characteristic, laterally spreading morphology.