BTK and breast carcinoma: It has been demonstrated that gain-of-function mutations introduced experimentally in the PH domain provide BTK with transforming potential;2, 5, 6, 7 however, no constitutively active BTK mutants have been identified so far in hematopoietic neoplasias, although it has been extensively shown that p77 plays pro-survival and anti-apoptotic roles in B cells.2, 3 Recently, a 80-kDa isoform, bearing an extended N-term, has been identified by Eifert et al.24 in breast carcinoma cells having, similar to p77BTK, pro-survival and anti-apoptotic roles.