NOTCH2 is one of the most frequently (10% to 25%) mutated genes in SMZL,[12] whereas NOTCH2 mutations are not found in chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), low grade follicular lymphoma (FL), or hairy cell leukemia (HCL).[13,14] The frameshift/deletion mutation we found in this case affects the C-terminal PEST domain of NOTCH2, which is critical for NOTCH2 proteasomal degradation. This evidence concerns the gene NOTCH2 and hairy cell leukemia.