Pure Well-differentiated Adenocarcinoma as a Safe Factor for Lymph Node Metastasis and Recurrence of T1 Colorectal Cancer.

Objectives: Pure well-differentiated adenocarcinoma (PWDA) could be a safe factor against lymph node metastasis (LNM) and recurrence in patients with T1 colorectal cancer. We investigated the utility and endoscopic features of PWDA to determine its predictive ability. Methods: We analyzed the LNM and recurrence rates, along with various clinicopathological factors, including PWDA, in 315 patients with T1 colorectal cancer who underwent surgical resection at our center. PWDA was defined as a lesion consisting of well-differentiated adenocarcinoma only. Three pathologists evaluated the consistency of the PWDA diagnosis and performed inter- and intraobserver assessments of PWDA and lymphatic invasion. Endoscopic features of PWDA was also examined. Results: The LNM, recurrence, and PWDA rates in patients with T1 colorectal cancer were 9.5%, 2.9%, and 31.1%, respectively. Significant differences were observed in T1b (100% vs. 82.8%; p = 0.014) and non-PWDA (100% vs. 65.6%; p < 0.001) between patients with and without LNM. Multivariate analyses showed that non-PWDA was an independent risk factor for LNM (odds ratio [OR], 12.09; 95% confidence interval [CI], 1.59-92.0; p = 0.016). Furthermore, significant differences in venous invasion (44.4% vs. 19.6%; p < 0.001), and non-PWDA (100% vs. 68.0%; p < 0.001) were observed between patients with and without recurrence. The agreement among three pathologists on the diagnosis of PWDA was acceptable (kappa value > 0.5). Surface redness (p < 0.001), a rugged surface (p < 0.01), fold convergence (p < 0.001), and an impression of fullness (p = 0.031) were significantly related with PWDA. Conclusions: PWDA can predict safety against LNM and recurrence in patients with T1 colorectal cancer.