Poorly differentiated colorectal cancers: correlation of microsatellite instability with clinicopathologic features and survival.

Abstract

To evaluate the association of microsatellite instability (MSI) with clinicopathologic features and oncologic outcomes in patients with poorly differentiated colorectal cancer (PD). Study patients were divided into well-differentiated colorectal cancer (WD) and PD, which were compared according to histologic differentiation and MSI status. Among 1,941 patients, PD was more frequent among microsatellite-unstable tumors (23.6%) than among microsatellite-stable (MSS) tumors (4.2%, P < .001). Patients with PD had worse 4-year overall survival rates than patients with WD (78.6% vs 88.2%, P = 0.010). Compared with MSS-PD tumors, MSI-PD tumors were characterized by right-colon predilection, larger size, and infrequent lymph node metastasis (P < .001 to P = .007). The clinicopathologic characteristics of PD were closely associated with those of MSI. The outcomes of MSI-PD tumors were better than those of MSS-PD tumors, but this finding did not reach statistical significance.