Komori et al. showed that stimulation by the proinflammatory cytokine tumor necrosis factor-alpha was associated with aberrant expression of the mutagenic enzyme activation-induced cytidine deaminase (AID) in human cholangiocarcinoma-derived cells resulting in somatic mutations of several genes including TP53, KRAS, and MYC [17]. The gene discussed is KRAS; the disease is cholangiocarcinoma.