The only difference in classifying a benign vs. malignant brain tumor is the speed of it's growth. is this really true?

Brain Tumor, B or M?: Definitive classification of a benign vs. Malignant brain tumor can only be made with absolute certainty based on the histologic features of the brain tumor. Speed of tumor growth may be suggestive but not reliable. A very low-grade malignant brain tumor may grow very slowly like the benign ones. Keep in mind, a biologically benign brain tumor can still cause serious damage given its location.