In contrast, MES-GSCs deploy EGFR/EGFRvIII-containing EVs that possess endothelial stimulating activity and trigger responses that may lead to circumferential extension of tumour blood vessels, a process that we termed vasectasia. In the latter case, our morphometric analysis of evolving vascular patterns post-tumour cell inoculation indicated a progressive increase in vessel diameter beginning at the boundary between brain parenchyma and MES-GSC-driven tumour masses, a change that extended toward tumour interior. Here, EGFR is linked to neoplasm.