SDHC and ductal breast carcinoma in situ: Base mutations in chr4:184562622 and chr7:35840881 were located at the exon splicing sites and led to an abnormal post-transcriptional splicing of RWDD4 and SEPT7. SDHC mutations occurred in Sum102 and Sum225 cell lines at the same mutant site, as well as SFN. RWDD4 and SEPT7 mutations occurred in both MCF10.DCIS and Sum102 cell lines.