We studied 25 cases of minute (less than 5 mm in a diameter) superficial depressed neoplastic lesions during the period of March 1990 to September 1991. These depressed neoplastic lesions were recognized by colonoscopy as asteroid redness with surrounding elevation. The thickness and height of the surrounding elevations were modified by air volume. Occasionally, they seemed according to the air volume to be elevated lesions, though their fundamental form was confirmed as being superficial depressed lesions from observations of histopathological sections and using a dissecting microscope. The endoscopic figures were emphasized by sprinkling them with Methylene Blue.
All of the minute depressed neoplastic lesions were histopathologically diagnosed as being tubular adenoma. For the purpose of confirming the histopathological character of the depressed neoplastic lesions (n = 25) and distinguishing them from conventional elevated adenomas (n = 71) of the same diameter, we compared the incidences of glandular crowding, nuclear stratification, nuclear pleomorphism and loss of nuclear polarity in two groups. Glandular crowding and nuclear pleomorphism were recognized significantly more often in the depressed neoplastic lesions than in the elevated adenomas.
Although most of the minute depressed neoplastic lesions were fundamentally adenomas, because of their unique histopathologic character, they could give new insight into the development of colon cancer.
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.
Out of a total of 466 cases of early colorectal cancer, we analyzed 139 cases with submucosal invasion (sm cancer) according to tumor size, gross appearance, depth and degree of invasion, and the presence of adenoma components. Early colorectal cancers 11 ‐20 mm in diameter were the most common lesion in this group, and the percentage with sm cancer increased with tumor size. More than 70% of relatively small sm cancers, 6‐10 mm in diameter, had moderate or massive submucosal invasion similar to that found in large sm cancers. Only 35% of 6‐10 mm cancers had an adenoma component; the majority (65%) had no adenoma component. In marked contrast, 63% of sm cancers 11 ‐20 mm in diameter had an adenoma component and in sm cancer the percentage of tumors composed solely of cancerous tissue without an adenoma component was low. Similar results were obtained when only protruding type sm cancers, which accounted for the majority of sm cancer cases, were included in the analysis. Therefore, we believe that the protruding type sm cancer 6‐10 mm in diameter is at a stage close to advanced cancer. It is possible that many 6‐10 mm sm cancers have a histogenesis different from that of large sm cancers.
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