The prevalence of gross del/dups has not previously been well described, with the exception of BRCA1/2 and Lynch syndrome genes.32,33 For a number of genes, del/dups accounted for greater than 10% of PVs, indicating that a substantial proportion of at-risk patients would be missed if del/dup testing methods are not included in MGPT. This evidence concerns the gene BRCA1 and Lynch syndrome.