The increased risk of breast cancer may result from a consequent ‘position effect’ of the translocation on the expression of a neighbouring breast cancer susceptibility gene(s).16 The 22q11.2 cannot be unambiguously assigned within a large 424 kb region; but the 11q23.3 breakpoint has been mapped to a region approximately 9 kb from APOA4,2 within a cluster of apolipoprotein genes. This evidence concerns the gene APOA4 and breast carcinoma.