Two large studies of DCIS (approximately 400 patients) have reported amplification of CCND1 in 10–12.6% of patients with pure DCIS and 14.8–17.4% of patients with DCIS associated with invasive breast cancer, with the majority of patients having amplification in the paired invasive component [39, 40]. The gene discussed is CCND1; the disease is ductal breast carcinoma in situ.