IDH2 is a mitochondrial enzyme involved in citrate metabolism. Mutations at Arg140 and Arg172 of IDH2 are typically heterozygous and are considered gain-of-function mutations that lead to increased levels of 2-hydroxyglutarate believed to alter epigenetic regulation in various tumors, especially in myeloid neoplasms. The Arg140 mutation of IDH2 has not been reported previously in lung tumors. However, a few other IDH2 mutations have been described in non-small cell lung cancers (NSCLC) in a very small number of patients in the literature. The prognostic impact of IDH2 mutations in NSCLC remains uncertain at this time. Mutant IDH2 may provide a potential therapeutic target in some settings. Clinical correlation is recommended.