Bao L, et al. - Using laser-capture microdissection (LCM) of single cells from H&E-stained tissue sections followed by single-cell sequencing and targeted duplex deep sequencing of pools of thousands of cells from different spatial locations of breast tumors, researchers sought to define the microheterogeneity and spatial distribution of intratumoral subclones and in primary tumor and synchronous lymph node metastasis. Copy number variations in several genomic regions, including areas within chr1p, chr8q, chr9p, chr12q, and chr20q, harboring several metastasis-associated genes were disclosed via gene mutations and copy number variations analyzed in 5 breast cancer tissue sample sets, that were consistently associated with lymph node metastasis. Data demonstrated clonal expansion in an area of morphologically normal breast epithelia, possibly driven by a driver mutation and a subsequent amplification in chr1q. Molecular evolution of breast cancer and genomic aberrations contributing to metastases were illustrated.