BRCA1 and neoplasm: A specific SNV spectrum, termed a mutagenic signature, has been associated with BRCA1/2 gene defects in tumour samples.11 When we compared all 30 currently documented tumour mutation signatures with the mean observed spontaneous mutation pattern of each cell line, it was apparent that the mutation pattern in the BRCA1−/− and BRCA2−/− cell line samples showed strongest correlation with the BRCA1/2 tumour associated ‘signature 3' (Figure 5a) and with each other (Figure 5b).