Histopathological studies of superficial-type early colorectal carcinoma

Superficial-type early colorectal carcinoma (SCa) is presently not a rare finding and is very important in discussions regarding the development of large bowel cancers, although the histologic characteristics of SCa remain obscure.

Using 54 SCa lesions (34 intramucosal adenocarcinomas (SCa-m) and 20 adenocarcinomas with invasion to the submucosa (SCa-sm)), the largest dimension of the depressed region of the lesion and the greatest dimension of the entire lesion were measured by the computed image analyzer, and the expression of p53 and ras of SCa were examined immunohistochemically.

The percent of depressed regions in SCa lesions measuring less than 5 mm in greatest extent was larger than in those measuring more than 6 mm, and the percent of depressed regions in SCa-sm with deeper carcinoma invasion was lower than that of SCa-sm with shallower invasion. There was a positive correlation between the depth of invasion and the maximum dimension of the carcinoma. The frequency of association with adenoma in all SCa-m was 21% and was 32% in SCa-m that were more than 6 mm in greatest extent, although all minute SCa-m lesions less than 5 mm were pure carcinomas without any adenomatous component. Positive expression of ras was noted in 41% of SCa-m and 36% of SCa-sm, respectively, while positive expression of p53 was noted in 63% of SCa-m and 88% of SCa-sm, respectively.

These results suggested that 70% to 80% of SCa developed via a de novo carcinoma theory and showed the depression form in the initial histologic stage and thereafter in the flat-protrusion form, while 20% to 30% of SCa arose from the preexisting flat adenoma via the adenoma-carcinoma sequence theory. The results also suggested that p53 was related to the enlargement and deeper invasion of SCa, regardless of the sequence of development of colorectal cancer.