Long-read sequencing enabled the team to reconstruct in great detail the history of how the HER2 gene gets massively amplified in HER2-positive breast cancer cells, says Dr. Schatz. Top rectangle shows a 2 million base-pair segment of chromosome 17 occupied by the HER2 gene (also called ERBB2). A small segment of the gene, already massively amplified, breaks off and fuses with chromosome 8 (lower rectangle). On that chromosome, parts of the gene are copied as many as 1000 times, with various segments jumping around within the chromosome (green arcs). This shows why we want to identify HER2-positive patients as early as possible, to prevent the kind of chaos that we register here cumulatively, says Schatz.