SF3B1 and mucosal melanoma: The SF3B1 gene, hence an essential protein in the U2 snRNP complex, is the most frequently mutated spliceosome gene and mutations are present in various malignant diseases such as UM [26], myelodysplastic syndromes (MDS) [31], chronic lymphocytic leukemia (CLL) [32], breast cancer [33], pancreatic cancer [34] and mucosal melanoma (especially in anorectal and vulvovaginal melanomas) [35].