ARHGAP21 and breast cancer: Some of these novel genes, such as CSNK2A1, ARHGAP21 and PRKACA have already been somehow implicated (genetic association, differential expression and mutation studies) in others types of cancers, namely neck squamous carcinoma [48], colorectal cancer risk [50], lung squamous cell carcinoma [51] and pituitary tumors [49]; while others, such as PPP2R5A, have not been studied in cancer, but may represent good biological candidates, given the involvement of other members of the known tumor suppressor phosphatase 2A family in ovarian, uterine and breast cancer risk [66,67].