SLX4 and breast cancer: In contrast, these 2 variants were also reported to have the same allele frequency, in two of the three previous SLX4 mutation screenings in BRCA1/2 mutation-negative breast cancer patients (10 [n = 52] and 8 [n = 94]) [18], [20] and were found to co-occur in 42 out of 526 patients in the third study [19].