Clinicopathologic features and prognosis of histologic subtypes in the right-sided colon cancer

Differentiation of the histopathologic subtypes can be clinically important as it can affect the course of treatment and the prognosis. The aim of this study was to investigate both the clinicopathological features and prognosis of histologic subtypes in right-sided colon cancer.

This study included 138 patients who underwent surgery for right-sided colon cancer. The patients were divided into three groups according to histopathological subtypes as follows: medullary carcinoma (MC, n=11), mucinous adenocarcinoma (MAC, n=29), and classic adenocarcinoma (AC, n=98). The groups were compared in terms of demographic characteristics, type of surgery, pathological outcomes and survival.

The rate of laparoscopic surgery was significantly lower in the MC group compared with MAC and AC groups (45.4% vs 54.5% vs 35.7%, respectively, p=0.001). In MC group, T4 stage was significantly higher than in other groups (90.0% vs 34.5% vs 35.7%, respectively, p=0.001). While patients with MAC had no distant metastasis, 18.2% and 15.3% of patients with MC and AC respectively, had distant metastasis (p=0.07). MAC vs MC, p=0.01, MAC vs AC, p=0.03). Tumor size, tumor volume, and the rate of microsatellite instability were found significantly higher in the MC group (p<0.05). The 5-year overall (OS) and disease-free survival (DFS) were better in the MAC group compared with MC and AC groups, but these differences did not reach statistical significance (OS: 92.8% vs 72.7% and 68.7%, p=0.16 and DFS 87.3% vs 58.2% and 64%, p=0.10, respectively).

MC is associated with more advanced tumor size and T stages, and therefore entails reduced rate of minimally invasive procedures. In our series, the absence of distant metastasis in the patients of MAC also had a positive effect on survival.