ALDH1A1 and ductal breast carcinoma in situ: Our findings suggest that OA might be a critical risk factor to promote the progression of DCIS to invasive breast cancer, and the ALDHhigh subpopulation with BCSC characteristics expressing a high level of ALDH1 and CD44 in DCIS of breast cancer may contribute to early invasion and migration in response to OA, possibly in association with the FAK and PI3K/AKT signaling pathway.