INTRODUCTION: In 2016, the WHO classification of diffuse astrocytoma began to include isocitrate dehydrogenase (IDH) mutation in addition to histology.

RESULTS: We here demonstrate a case where a 14-year-old boy presented with a parietal tumor with no histological evidence of neoplasia but with an IDH1 mutation. Due to the IDH1 R132H mutation, the patient was diagnosed with diffuse astrocytoma WHO grade II and underwent successful gross total resection of this near-eloquently located tumor.

CONCLUSION: This case exemplifies how inclusion of immunohistochemistry in tumor classification alters surgical strategy and might improve accuracy and time to diagnosis.