BCR and B-cell chronic lymphocytic leukemia: BCR signaling plays a critical role in CLL pathogenesis (Burger & Chiorazzi, 2013), and, accordingly, inhibitors targeting BCR‐associated kinases [Bruton's tyrosine kinase (BTK), phosphoinositide 3‐kinase (PI3K) δ] have shown great clinical efficacy in patients (Burger & Chiorazzi, 2013; Furman et al, 2014).