We previously reported the CINSARC signature as a prognostic marker for metastatic events in soft tissue sarcomas, breast carcinomas and lymphomas through genomic instability, acting as a major factor for tumor aggressiveness. In this study, we used a published resource to investigate CINSARC enrichment in poor outcome-associated genes at pan-cancer level and in 39 cancer types. CINSARC outperformed more than 15,000 defined signatures (including cancer-related), being enriched in top-ranked poor outcome-associated genes of 21 cancer types, widest coverage reached among all tested signatures. Independently, this signature demonstrated significant survival differences between risk-groups in 33 published studies, representing 17 tumor types. As a consequence, we propose the CINSARC prognostication as a general marker for tumor aggressiveness to optimize the clinical managements of patients.