SOX9 and ductal breast carcinoma in situ: When examined at 3–4 months of age, Sox9-cKO and control C3(1)/Tag mice showed no significant difference in the formation of mammary intraepithelial neoplasia (MIN), noninvasive lesions similar to ductal carcinoma in situ (DCIS) in human breast cancer, indicating Sox9 deficiency does not affect early-stage hyperplasia (Figures 4A and 4B).