COL1A1 and cancer: Here, we applied Scissor (single‐cell identification of subpopulations with bulk Sample phenotype correlation) to integrate single cell and bulk data of breast cancer, and found that MHC‐deficient tumor cells, FABP5+ macrophages, and COL1A1+ cancer‐associated fibroblasts (CAFs) were detrimental to patient survival, while T cells and dendritic cells were the main protective cells.