BTK and marginal zone lymphoma: The introduction of inhibitors of phosphatidylinositol 3-kinase (PI3K) and Bruton tyrosine kinase (BTK) has represented a big step forward in the treatment of patients affected by indolent B cell lymphomas, including marginal zone lymphoma (MZL) and lymphoplasmacytic lymphoma (LPL) [1,2,3,4,5,6,7].