Simple SummaryColorectal cancer (CRC) is one of the most prevalent cancers, and approximately a quarter of patients diagnosed at stage II exhibit a significant risk of recurrence. In this study, we successfully identified a microRNA (miRNA) signature allowing the recognition of patients at high recurrence risk. The validity of these findings has been confirmed through an entirely separate group of patients diagnosed with stage II microsatellite stability (MSS) colon adenocarcinoma (COAD). Most of the miRNAs present in the signature have demonstrated prognostic relevance in various other cancer types. Upon examining their gene targets, we discovered that some of these miRNAs are intricately involved in pivotal pathways of cancer progression.AbstractWe aimed to identify and validate a set of miRNAs that could serve as a prognostic signature useful to determine the recurrence risk for patients with COAD. Small RNAs from tumors of 100 stage II, untreated, MSS colon cancer patients were sequenced for the discovery step. For this purpose, we built an miRNA score using an elastic net Cox regression model based on the disease-free survival status. Patients were grouped into high or low recurrence risk categories based on the median value of the score. We then validated these results in an independent sample of stage II microsatellite stable tumor tissues, with a hazard ratio of 3.24, (CI95%= 1.05–10.0) and a 10-year area under the receiver operating characteristic curve of 0.67. Functional analysis of the miRNAs present in the signature identified key pathways in cancer progression. In conclusion, the proposed signature of 12 miRNAs can contribute to improving the prediction of disease relapse in patients with stage II MSS colorectal cancer, and might be useful in deciding which patients may benefit from adjuvant chemotherapy.