Abstract H3 K27M-mutant diffuse gliomas without midline involvement are extremely rare and their clinical behavior remains elusive due to limited reported follow-up data. We describe an H3 K27M-mutant diffuse non-midline glioma patient with extended follow-up. A 34-year-old woman presented with headache, memory loss, periods of changes in taste and smell, and confusion. Imaging studies revealed an 2.3 cm expansile T2/flair hyperintensity with patchy postcontrast enhancement centered in the left amygdala without associated restricted diffusion and no involvement of the midline structures. The tumor was debulked and consisted of a mitotically active infiltrating astrocytic glioma without tumor necrosis or microvascular proliferation, consistent with anaplastic astrocytoma. Targeted 187-gene neuro-oncology NGS testing detected an H3F3A K27M mutation along with a PTPN11 and a PPM1D mutation. FISH 1p/19q-codeletion testing was negative. MGMT promoter was unmethylated. The patient was treated with chemoradiation with temozolomide for 6 weeks followed by 12 cycles of temozolomide. Four years after initial resection, an area of increased post-contrast enhancement indicating tumor recurrence/progression was noted. Partial resection of the recurrent tumor revealed a mitotically active infiltrating astrocytic glioma with tumor necrosis consistent with glioblastoma. Molecular profiling of the recurrent tumor by the neuro-oncology NGS panel detected similar mutational profile (identical H3F3A K27M and PTPN11 mutation; different PPM1D mutation) with an additional SOS1 mutation. The patient completed 4 cycles of Lomustine and although clinically stable, imaging studies showed slight increase in residual tumor size concerning for tumor progression. Lomustine was discontinued, Bevacizumab therapy was initiated and patient was enrolled in clinical trial (NCT02525692). Despite tumor progression, this patient has had a relatively long disease course (5 years) suggesting that H3 K27M-mutant non-midline diffuse gliomas although molecularly similar, may follow a more favorable clinical course than their midline counterparts possibly due to the hemispheric location, which is more amenable for surgical resection.