Slow-Growing Thalamic Glioma with Histone H3 Lysine 27-to-Methionine Mutation: 3-Year Follow-Up Before Surgical Intervention.

BACKGROUND: The 2016 World Health Organization Classification of Tumours of the Central Nervous System was revised to include a new diagnostic entity, diffuse midline glioma, H3 K27M-mutant (DMG-K27M), a highly aggressive tumor with a mean survival time of 1 year after diagnosis. DMG-K27M is classified as a World Health Organization grade IV tumor regardless of histopathologic features, and there is currently no effective treatment for it despite ongoing research. CASE DESCRIPTION: We present a case of a 39-year-old man with a slow-growing thalamic glioma with histone H3 lysine 27-to-methionine mutation. This patient received surgical intervention 3 years after the initial discovery of the tumor. Because the patient did not receive any preoperative treatment for DMG-K27M, this case reflects 1 possible natural course of progression for this type of malignancy. CONCLUSIONS: There are currently no effective therapeutic options for treatment of DMG-K27M. The slow tumor growth and prolonged survival time (≥ 3 years) in the absence of intervention in this case serve as a reminder that much is still not known about histone H3 lysine 27-to-methionine mutation and how it impacts the pathophysiology, diagnosis, treatment, and prognosis of the disease. Careful evaluation is warranted to determine if early intervention is the best approach when treating DMG-K27M.