CD44 and neoplasm: Strikingly, we found that 88% (7/8) of an unbiased sample of 8 primary human GBM tumors show abnormally elevated levels of CDC42 and CD44, restricted to perivascular locations on abnormal blood vessels at the boundary between tumor tissue and normal looking brain (Figure S10 A–C), a feature reproduced in an independent GBM biopsy (Figure S10 E).