PIK3CA and neoplasm: Through the integration of multi-omics data, in vitro coculture models, clinical cohort analysis, and mechanistic exploration, this study aims to: (1) analyze the core role of FN1 in CAF-tumor cell interactions; (2) elucidate the molecular mechanisms by which FN1 regulates the PI3K/AKT pathway and the immune microenvironment; (3) evaluate the translational potential of FN1 as a prognostic biomarker and therapeutic target.