JAK1 and breast cancer: Indeed, a PCR-single strand conformation polymorphism (SSCP) assay revealed 3 mutations in 90 BC cases: 1 mutation in JAK1 c.1939C>T (p.H647Y), 1 mutation in JAK3 c.2143G>A (p.V715I) and 1 mutation in JAK3 c.420+28G>A (unknown) [90].