Despite their importance, little is known about the natural history of non-polypoid colorectal neoplasms (NP-CRN). This article will summarize the available data to gain some estimates of the natural history of NP-CRN.
The importance of non-polypoid colorectal neoplasms (NP-CRN) is now recognized throughout the world. There is little information, however, known about the natural history of NP-CRN, perhaps because the initial reports of NP-CRN suggested that it had high risk of invasion and lymph node metastasis as compared with polypoid lesions of similar size. Long-term follow-up of NP-CRN without resection was therefore not an accepted treatment strategy, and had been reported only based on analysis of interval neoplasms or sporadic case reports. In addition, outside Japan, many endoscopists viewed NP-CRN, especially the depressed lesion, as a uniquely Japanese phenomenon and thus, paid little attention to such lesions, limiting the data even more. This article will summarize the available data to gain some estimates of the natural history of NP-CRN.
Radiographic analysis
Matsui and colleagues reported a retrospective analysis of a series of colorectal cancers that were missed by double-contrast barium enema examinations. They found six depressed and seven flat lesions (41%) could be retrospectively identified as antecedent lesions that gave rise to 32 advanced cancers. The authors found that all depressed lesions developed into nonprotuberant-type advanced colorectal cancers, whereas flat or polypoid lesions had a possibility to develop into either protuberant or nonprotuberant-type advanced colorectal cancers.
Umetani and colleagues reported 11 cases of colorectal cancers that had more than two barium enema examinations that were at least 6 months apart. Five non-polypoid submucosal invasive cancers were studied; three developed from non-polypoid and two from polypoid lesions. The authors estimated tumor doubling time to evaluate the growth rate of each tumor, and suggested that NP-CRN grew slowly compared with polypoid lesion and maintained their macroscopic morphology. The data, however, are limited.
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Non-Polypoid Colorectal Neoplasms are Relatively Common Worldwide
Endoscopic Mucosal Resection of Non-Polypoid Colorectal Neoplasm
Dynamic Submucosal Injection Technique
Targeted Imaging of Flat and Depressed Colonic Neoplasms
Endoscopic Submucosal Dissection of Non-Polypoid Colorectal Neoplasms
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