The significance of the state of muscularis mucosae (MM grade) as a new risk factor for nodal metastasis in considering the indication for additional surgical colectomy with lymph node dissection among submucosal-invasive (T1) colorectal carcinomas after endoscopic treatment - The significance of the state of muscularis mucosae (MM grade) as a risk factor for nodal metastasis in considering the indication for additional surgical colectomy among T1 colorectal carcinomas after endoscopic treatment

Results: MM grade was associated with nodal metastasis (p = 0.026), and no patients with MM grade 1 lesions had nodal metastasis. Significant risk factors for nodal metastasis in patients with MM grade 2 lesions were attribution of female (p = 0.006), lymphovascular infiltration (p < 0.001), tumor budding (p = 0.045), and poorly differentiated adenocarcinoma or mucinous carcinoma (p = 0.007). Nodal metastasis occurred in 1.06% of lesions without any of these pathological factors, but in 10.3% and 20.1% of lesions with at least one factor in male and female patients, respectively. There was good inter-observer agreement for MM grade evaluation, with a kappa value of 0.67. Conclusions: Stratification using MM grade, pathological factors and patient sex provided more appropriate indication for additional surgery with lymph node dissection after endoscopic treatment for T1 colorectal carcinomas.