Multiple lesions, including multifocal and multicentric GBM, are found in 0.5%–35% of all GBMs13–17 and are associated with a worse prognosis than solitary lesions.14 Several major genetic variants, including PTEN loss, TERT mutation,18 and EGFR mutation,19 are found in multiple lesions in GBMs. The gene discussed is PTEN; the disease is glioblastoma.