RAC1 has been mostly regarded as a cancer cell‐intrinsic factor involved in the proliferation and migration of cancer cells.[18, 19, 21] To elucidate how Rac1a and Rac1b affect the characteristics of tumor cells, we performed single‐cell RNA sequencing on dissected tumors and analyzed the epithelial cells, which comprise malignant tumor cells and their progenitors. The gene discussed is RAC1; the disease is cancer.