Expression of these exons was detected (Supplementary Table 3)—clearly in two cases, FAM91A1-NRG1 and ARHGEF39-NRG1 but not conclusively in the other two cases where there were too few reads overall—but we could not tell whether these reads were from fusion transcripts or normal transcripts, from tumour or normal cells. The gene discussed is ARHGEF39; the disease is neoplasm.