ARID1A and cancer: Somatic ARID1A variants, often heterozygous (44), have previously been found in atypical carcinoid tumors (6, 39) and have also been implicated in the pathogenesis of numerous other cancer types due to the role of ARID1A in the SWI/SNF chromatin remodeling complex (45), where ARID1A variants cause increased cell proliferation, migration, and invasion through a variety of mechanisms (46).