The study of two patients (one with ER+ and the other with TNBC) showed: (i) in both patients, a large number of subclonal and de novo mutations gradually evolved over long periods of time, thus generating extensive clonal diversity; and, (ii) in contrast, the single cell copy number profiles were highly comparable, suggesting that chromosome rearrangements occurred early during tumor development, according to punctuated bursts of tumor evolution, leading to stable clonal expansions required for tumor mass formation [53]. This evidence concerns the gene ESR1 and neoplasm.