Mucinous adenocarcinomas are uncommon and signet-ring cell carcinomas are rare histological subtypes of colorectal cancer, which differ from classical adenocarcinomas in clinicopathology and prognosis. In particular, signet-ring cell carcinomas could be taken into account for individual risk estimation because of their clearly different behavior.

Background:Patients with UICC/AJCC stage II colon cancer have a high 5-year overall survival rate after surgery. Nevertheless, a significant subgroup of patients develops tumour recurrence. Currently, there are no clinically established biomarkers available to identify this patient group. We applied reverse-phase protein arrays (RPPA) for phosphatidylinositide-3-kinase pathway activation mapping to stratify patients according to their risk of tumour recurrence after surgery.Methods:Full-length proteins were extracted from formalin-fixed, paraffin-embedded tissue samples of 118 patients who underwent curative resection. RPPA technology was used to analyse expression and/or phosphorylation levels of six major factors of the phosphatidylinositide-3-kinase pathway. Oncogenic mutations of KRAS and BRAF, and DNA microsatellite status, currently discussed as prognostic markers, were analysed in parallel.Results:Expression of phospho-AKT (HR=3.52; P=0.032), S6RP (HR=6.3; P=0.044), and phospho-4E-BP1 (HR=4.12; P=0.011) were prognostic factors for disease-free survival. None of the molecular genetic alterations were significantly associated with prognosis.Conclusions:Our data indicate that activation of the PI3K/AKT pathway evidenced on the protein level might be a valuable prognostic marker to stratify patients for their risk of tumour recurrence. Beside adjuvant chemotherapy targeting of upregulated PI3K/AKT signalling may be an attractive strategy for treatment of high-risk patients.

Background/Aims: Recent data suggest that tumors of the right and left colon should be distinguished as they differ in clinical and molecular characteristics. Methods: A total of 1,319 patients who underwent surgical resection for colon cancer (CC) were investigated. Tumors between the ileocecal valve and the hepatic flexure were classified as right CC (RCC), tumors between the splenic flexure and the rectum as left CC (LCC). Results: RCC revealed a higher cause-specific mortality risk (hazard ratio 1.36, 95% CI 1.10-1.68, p = 0.005) and lower 5-year cause-specific (RCC 64.9%, 95% CI 60.4-69.4, LCC 70.7%, 95% CI 67.2-74.2, p = 0.032) and disease-free (RCC 56.0%, 95% CI 51.5-60.5, LCC 59.9%, 95% CI 56.2-63.6, p = 0.025) survival rates. RCCs were more often microsatellite instable (RCC 37.2%, LCC 13.0%, p < 0.001) and more often showed KRAS (RCC 42.5%, LCC 18.9%, p = 0.001) and BRAF mutations (RCC 26.6%, LCC 3.2%, p < 0.001). Conclusion: RCC and LCC differ significantly regarding clinical, histopathological and molecular genetic features and can be considered as distinct entities. The reduced prognosis of RCC may be caused by higher rates of microsatellite instability, KRAS and BRAF mutations.