Present Status of Early Colorectal Cancer in Japan

Abstract

We examined and clinicopathologically analyzed 422 patients with early colorectal cancer that we encountered, and discussed the problems typical of early colorectal cancers in Japan. In Japan we define early colorectal cancer as consisting of intramucosal cancer and cancer with submucosal invasion. Because histopathologists subjectively diagnose patients with intramucosal cancer, their diagnoses for the same specimen often differ from each other. The only way to avoid such confusion caused by diagnostic differences and to reach a consensus on the diagnosis of intramucosal cancer is to make a diagnosis of intramucosal cancer only in those patients who clearly show the structural atypia and/or the cellular atypia, that are typical of cancer. No one will deny the importance of the depressed type early cancer, the number of cases of which have recently been increasing in Japan. However, it is also important to assert that endoscopically‐discovered depressed neoplastic lesions are not always cancer. In the depressed neoplastic lesions discovered in our patients, the number of adenoma was almost three times that of cancer. Forty percent of the patients with depressed type early cancer also had an adenoma component. Therefore, at this moment we cannot conclude that early cancer with a depression is de‐novo‐genetic colorectal cancer. Eighty percent of early colorectal cancers are discovered to be the protruded type of early cancer. Twenty‐six percent of early cancers with submucosal invasion, including early cancers with massively submucosal invasion, are 6 to 10 mm in diameter and 76% of these are protruded early cancers. These facts indicate that colorectal tumors, protruded or depressed, which are more than 6 to 10 mm in diameter should be endoscopically removed to prevent them from becoming advanced cancers.

Is the Histogenesis of 6‐10 mm Early Colorectal Cancer Different from that of Larger Cancers?

“…When only the protruding type sm cancers were analyzed, i. e., with exclusion of the depressed and the superficial elevated types, no adenoma component was found in 60% of 6-10 mm lesions, in contrast to 36.5% of 11-20 mm lesions and 47.6% of those 2 2 1 mm. The percentage of 6-10 mm lesions without adenoma components was significantly higher than that of [11][12][13][14][15][16][17][18][19][20] mm lesions (p < 0.05, x test). However, the lesions 2 21 mm were too few for statistical analysis.…”

Histoclinical Analysis of Early Colorectal Cancer

“…Many studies, mainly undertaken in Japan, show that an ECC rate as high as 20% of all colorectal cancer [2][3][4] is mainly due to the wider distribution of mass screening. It provides a successful model for mass screening for colorectal cancer.…”