IDH-mutant tumors have aberrant production and accumulation of the oncometabolite 2-hydroxyglutarate (2-HG), which may play a pivotal oncogenic role in several malignancies. A case of an IDH1 p.R132L mutation in a patient with hormone receptor-positive (HR+) breast adenocarcinoma has been reported (5). IDH1 mutations may impact a rare subgroup of patients with breast adenocarcinoma, suggesting future avenues for disease monitoring through noninvasive measurement of 2-HG, as well as for the development and study of targeted therapies against the aberrant IDH1 enzyme.