Clinical significance of the muscle-retracting sign during colorectal endoscopic submucosal dissection.

BACKGROUND AND STUDY AIMS: During colorectal endoscopic submucosal dissection (ESD), the feature of a muscle layer being pulled toward a neoplastic tumor is sometimes detected. We call this feature the muscle-retracting sign (MR sign). The aim of this study was to evaluate whether the MR sign is associated with particular types of neoplastic lesions and whether it has any clinical significance for ESD sessions. PATIENTS AND METHODS: A total of 329 patients underwent ESD for 357 colorectal neoplasms. The frequency of positivity for the MR sign was evaluated in different morphologic and histopathologic types of neoplasm. The success rate of complete resection and the incidence of complications were also evaluated according to whether lesions were positive or negative for the MR sign. RESULTS: The rates of positivity for the MR sign in the various lesion types were as follows: laterally spreading tumor - granular nodular mixed type (LST-G-M), 9.6 %; laterally spreading tumor - granular homogeneous type (LST-G-H) and laterally spreading tumor - nongranular type (LST-NG), 0 %; sessile type, 41.2 %. The resection rate was 100 % (329 /329) in lesions negative for the MR sign; however, it was 64.3 % (18 /28) in lesions positive for the MR sign, which was significantly lower (P < 0.001). CONCLUSIONS: The MR sign was present only in some protruding lesions, and more importantly, it was associated with a high risk of incomplete tumor removal by ESD. Our data indicate that lesions positive for the MR sign lesions should be dissected with great caution; alternatively, based on the features of the individual case, a switch to surgery should be considered for the benefit of the patient.