Background: Somatic mutations at adenomatous polyposis coli (APC) gene, found in ~75% of colorectal cancers (CRC), are under-represented in microsatellite instable (MSI-H) tumors. While several studies have suggested worse outcomes for CRC patients (pts) with wild-type APC (APC-WT), the prognostic implication of this genomic alteration in metastatic CRC (mCRC) is not well defined. Methods:APC prognostic value was evaluated in 331 stage IV microsatellite stable (MSS) CRC pts treated in our institution. Next-generation genomic analysis (FoundationOne) was used to characterize the molecular characteristics of APC-WT and mutant APC (APC-MT) pts. Findings were validated on a public database of stage IV colon cancer from MSKCC. Results:APC-WT was present in 26% of mCRC patients. In comparison to APC-MT population (n = 244), APC-WT pts (n = 87) tended to be younger (median age: 49 vs. 58 years), right-sided (44% vs. 24%), BRAF-V600E mutated (25% vs. 5%), p53 WT (38% vs. 21%) and RAS WT (66% vs. 53%). APC-WT tumors were associated with other Wnt activating alterations (CTNNB1, FBXW7, RNF43, ARID1A and SOX9). Among those, RNF43 and CTNNB1 were more significantly represented in the APC-WT vs APC-MT population (12% vs 1% and 11% vs 3%, respectively). APC-WT pts had a worse overall survival (OS) than APC-MT pts (30 vs 48 months, HR = 1.809, 95% CI 1.260-2.596, p < 0.0001). Using a multivariate model correcting for primary tumor location, RAS and BRAF status, APC-WT was predictive of poor survival (HR = 1.7, p = 0.001) in our data set. The prognostic implication of APC-WT on OS were confirmed further in a similar multivariate model of 433 stage IV pts from MSKCC public database (HR = 1.6, P = 0.01). Conclusions:APC-WT is associated with poor OS in MSS mCRC regardless of RAS, BRAF status. Compared with APC-MT mCRC tumors, APC-WT tumors were associated with other activating alterations of Wnt pathway, including RNF43 and CTNBB1.