The truncating and splice site mutations in the ARID1A (non-core AT-rich interactive domain 1A) gene encoding the BAF250A subunit of SWI/SNF CRC were reported in about 26% of HL patient samples, analyzed by the whole-exome sequencing of flow cytometry–sorted HRS cells from 23 excisional biopsies. The gene discussed is ARID1A; the disease is colorectal carcinoma.