Consistently, NOTCH2 haploinsufficiency results in a severe reduction of splenic marginal zone B cells in Notch2+/f, CD19-Cre (Notch2+/−) mice models [101], while gain-of-function NOTCH2 mutations occur in 10–25% of splenic marginal zone lymphomas (SMZLs) [102,103]. This evidence concerns the gene NOTCH2 and splenic marginal zone lymphoma.