TERT Immunohistochemistry as a Surrogate Marker for TERT Promoter Mutations in Infiltrating Gliomas.

Genomic alterations are critical for the diagnosis, prognostication, and treatment of patients with infiltrating gliomas. Telomerase reverse transcriptase promoter (TERTp) mutations are among such crucial alterations. Although DNA sequencing is the preferred method for identifying TERTp mutations, it has limitations related to cost and accessibility. We tested telomerase reverse transcriptase (TERT) immunohistochemistry (IHC) as a surrogate for TERTp mutations in infiltrating gliomas. Thirty-one infiltrating gliomas were assessed by IHC using an anti-TERT Y182 antibody. IHC results were analyzed by a board-certified neuropathologist. Tumors were analyzed by targeted next-generation sequencing. A literature review of the use of TERT antibodies as a surrogate for TERTp mutations was performed. Eighteen gliomas harbored TERTp mutations. Overall, TERT IHC demonstrated a sensitivity of 61.1% and a specificity of 69.2% for identifying TERTp mutations. Among the 19 IDH1/IDH2-wild-type gliomas, 16 (84%) harbored TERTp mutations, and TERT IHC had a sensitivity of 62.5% and a specificity of 33.3%. Among the 12 IDH1/IDH2-mutant gliomas, 2 (17%) harbored TERTp mutations, and TERT IHC had a sensitivity of 50% and a specificity of 80%. TERT IHC had low positive and negative likelihood values in the identification of TERTp mutations. The literature review included 5 studies with 645 patients and 4 different TERT antibodies. The results consistently showed poor sensitivity and specificity of TERT IHC for identifying TERTp mutations. TERT IHC is a suboptimal surrogate marker for TERTp mutations in infiltrating gliomas. The need remains for cost-effective, efficient, and accessible alternatives to next-generation sequencing for the evaluation of TERTp mutations in gliomas.