IDH1 Expression via the R132H Mutation–Specific Antibody in Adrenocortical Neoplasias—Prognostic Impact in Carcinomas

CONTEXT: Mutations to isocitrate dehydrogenase (IDH) appear to play a prognostic or predictive role in several neoplasias. Immunohistochemical staining designed to detect a specific R132H mutation to IDH1 showed expression in the normal adrenal cortex, raising interest to study the potential role of IDH1 in the pathogenesis of adrenocortical tumors. OBJECTIVE: The objective of this work is to study the role of IDH1 and its mutations in adrenocortical tumors. DESIGN AND PATIENTS: IDH1 R132H immunohistological staining was performed on a cohort of 197 adrenocortical tumors. The exon of the IDH1 gene was sequenced in 16 tumors. RESULTS: Positive IDH1 R132H immunohistochemical staining correlated with a better prognosis among patients with a malignant adrenocortical tumor. However, IDH1 R132H immunohistochemistry did not distinguish between local and metastasized tumors. We were unable to identify IDH1 mutations among our adrenocortical tumors using a targeted next-generation sequencing panel or via exon sequencing. CONCLUSIONS: Among adrenocortical carcinomas, IDH1 R132H immunopositivity correlated with a better prognosis. Thus, IDH1 R132H immunohistochemical staining could serve as a prognostic or as a potential predictive marker in adrenocortical carcinomas. Further research is needed to identify the possible alterations in IDH1 that could explain our findings, because we identified no known mutations to the IDH1 gene.