CTSB and meningioma: Our study also confirms that higher expressions of cathepsins B and L correlate with a higher meningioma grade, as already shown in previous studies.26–28 However, since invasiveness is also found in BM, the meningioma grade is probably not directly correlated to expression of cathepsins B and L. Several cellular mechanisms of cellular proliferation, invasiveness and others are responsible for the malignant transformation of meningiomas.