Management of Colorectal Cancer Less Than 10mm in Diameter On the Basis of Pit Pattern Diagnosis

Abstract

Background and Aims: In most cases, small colorectal neoplasms can be endoscopically resected in one piece. However, we have recognized that some depressed type neoplasms invade the submucosal layer when they are very small. Endoscopic mucosal resection (EMR) should be performed after the precise prediction of the lesion depth. The aim of this study is to clarify the availability of pit pattern diagnosis for small colorectal lesions and the significance of EMR as a means of excisional biopsy of the lesions. Methods: A total of 10212 colorectal neoplasms excluding advanced carcinomas were resected endoscopically or surgically from Apr. 2001 to Jun. 2008 in our unit. Those less than 10mm in diameter amounting to 7258 lesions were included in the study. The morphologic and pathological findings of these small lesions were analyzed from our data files. Results: Among the subjective lesions, 4535 cases (62.5%) were protruded type, 2651 cases (36.5%) and 72 cases (1.0%) were flat and depressed type lesions. The rates of submucosal invasion were 0.7% (30/4535) for protruded lesions, 0.2% (6/2651) for flat lesions and 45.8% (33/72) for protruded lesions. The difference in rates of submucosal invasion was significant (p<0.0001). Although depressed lesions are less frequent, they are characteristic for a high rate of submucosal invasion. In other words, depressed lesions have high potential for invading submucosal layer even when they are very small. As for the pit pattern of the lesions, type IIIL, IIIS, IV, VI and VN were recognized in 6070 (83.6%), 64 (0.9%), 961 (13.2%), 147 (2.0%) and 16 (0.2%) lesions, respectively. The comparison between the pit pattern and submucosal invasion showed that lesions with type IIIL, IIIS and IV were associated with very low rate (0.1%) of invasion. On the other hand, the respective rates of invasion in those with VI pit pattern and VN were 32.0% and 87.5%. Lesions with VN pit pattern and depressed lesions with VI pit pattern should be considered to be treated surgically because of their high rate of submucosal invasion (87.5% and 62.5%). Protruded or flat lesions with VI pit pattern can be treated endoscopically as the possible invasion is usually only slight. Conclusion: The precision of pattern diagnosis is high enough for small lesions. In most cases, depressed lesions with VI pit pattern and/or lesions with VN pit pattern should be treated surgically even if they are less than 10mm in diameter.