ALK and ovarian cancer: ALK positivity, as assessed by immunohistochemistry (IHC), is present in 20.9% and 36% of ovarian and breast cancers, respectively, and more prevalent in aggressive histological subtypes, such as high-grade serous ovarian cancer (HGSOC) (28% in HGSCO versus 0% in other ovarian cancer subtypes, P = 0.002) and triple-negative breast cancer (TNBC) (47% in TNBC versus 34% in non-TNBC, P = 0.0034)30,31.