We found that TP53 coding mutations and clonal losses of 3p, 4p, 5q, 8p, 13q, 14q, 16q, 17p, 17q, 21p, and 22q and gains of 1q, 8q, and 17q that were present in basal breast cancer were also detected in at least 20% of the DCIS samples, indicating that these chromosome-arm aberrations are key events in tumorigenesis (Figure S3A). This evidence concerns the gene TP53 and ductal breast carcinoma in situ.