Inactivating ARID1A mutations have been detected across a range of diverse cancer types (Kadoch et al., 2013), including 9.4% of colorectal carcinomas (Cancer Genome Atlas Network, 2012) and up to 60% of OCCCs (Jones et al., 2010; Wiegand et al., 2010). The gene discussed is ARID1A; the disease is cancer.