BTK and mantle cell lymphoma: Due to the criticality of Bruton’s tyrosine kinase (BTK) in BCR signaling, BTK is an important therapeutic target and as a result, several BTK inhibitors have been developed and have shown remarkable results in treating other B cell malignancies, such as chronic lymphocytic leukemia (CLL) [84,85], mantle cell lymphoma (MCL) [84], marginal zone lymphoma (MZL) [86], and Waldenström macroglobulinemia (WM) [86].