Given a frequency of approximately 20% BRCA1 methylation in invasive carcinoma [37], this suggests that tumours driven by BRCA1 methylation either rarely pass through a DCIS phase or have an exceedingly rapid transit through one, a notion supported by observation that DCIS is rare in carriers with BRCA1 germline mutations [38],[39]. The gene discussed is BRCA1; the disease is ductal breast carcinoma in situ.