Clinicians typically classify meningiomas — the most common type of brain tumor — into three grades, ranging from slow-growing to aggressive.

But a new multi-institutional study suggests that appearances may be deceiving. If a tumor shows activity in a gene called telomerase reverse transcriptase (TERT), it tends to recur more quickly, even if it looks low-grade under the microscope.

Researchers discover that when meningiomas, a type of brain tumor, shows activity in the TERT gene, it tends to recur more quickly.