Conflicting Finding on Intramucosal Colon Cancers Based on National Survival Outcomes Data

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TO THE EDITOR: The article by Gunderson et al provides powerful evidence to support the revised staging system in the seventh edition of the American Joint Committee on Cancer (AJCC) Cancer Staging Manual for colon cancer. The case numbers of national-based survival data are large enough to explore significant subtle staging factors. However, an interesting point about Tis colon cancers is worthy of deeper discussion, which was not mentioned in the article. We found the contents both in Table 1 and Table 2 in this article showed that a proportion of Tis colon cancers had lymph node metastasis, with a very low incidence. A total of 5,939 patients had Tis colon cancer, and 95 patients (1.6%) had N1 disease and 19 patients (0.32%) had N2 disease. This finding challenges our previous general rule that colon cancer confined to the mucosa has no chance of metastasis and thus no further treatment is needed. According to the previous AJCC consensus in 2000, colon tumors invading the lamina propria up to and including the muscularis mucosae have no associated risk of regional lymph node metastasis. However, recent data using immunohistochemical marker D2-40 have shown the presence of lymphatic channels extending to the colonic mucosa in neoplastic and inflammatory conditions. Literature on the subject of metastatic risk in intramucosal colorectal carcinoma is extremely limited. Only one patient with poorly differentiated intramucosal rectal cancer had recurrence after surgical resection. We reviewed the patient group in our hospital. In total, there were 3,196 patients with colorectal cancer who received treatment at our hospital during 1999 to 2005. Among the 118 patients receiving regional resection for Tis tumors, no lymph node metastasis was found, except in one patient with a polypoid lesion. The pathology slides of this patient were reviewed carefully, and the tumor was actually a T2 lesion that invaded the superficial muscle layer. In fact, certain types of intramucosal cancer can have lymph node metastasis in gastric cancer. In colorectal cancer, data are still lacking regarding lymph node metastasis in intramucosal tumors. We suggest that all pathologic slides of these intramucosal colon cancers with lymph node metastasis in this article should be reviewed carefully, if possible, to certify the actual invasion depth of the tumor. If it is true that lymph node metastasis could occur in intramucosal colon cancer, it will provide us with a new point of view concerning the treatment of this type of tumor. As a result of recent advances for endoscopic procedures, such as endoscopic mucosal resection or endoscopic submucosal dissection, local treatment for early colorectal cancers is generally accepted and widely applied. If intramucosal colon cancers could have risk of metastasis, additional investigation is warranted to define the high-risk group before applying local treatment for these patients.