It should, however, be mentioned that the application of next-generation sequencing technologies has detected cases with gain-of-function point-mutations in splicing factor genes, mainly the constitutive spliceosome factors, splicing factor 3b subunit 1 (SF3B1) and U2 small nuclear RNA auxiliary factor 1 (U2AF1), in myeloid cell malignancies and rare cases of breast or lung cancer [24,25,26]. The gene discussed is U2AF1; the disease is lung cancer.