Gain-of-function somatic KRAS mutations. (A) Cell subsets were sorted by flow cytometry and used for DNA sequencing; (B) Peripheral blood mononuclear cells (PBMCs) were lysed and used for DNA sequencing; a buccal swab was also sequenced to rule out a germline mutation. The small mutant peak seen in the buccal sample probably reflects the presence of hematopoietic cells in the cell mixture.