###### Abstract  
Primary and metastatic brain tumors are usually serious conditions with poor prognosis, which reveal the urgent need of developing rapid diagnostic tools and efficacious treatments. To achieve these objectives, progress must be made in the understanding of brain tumor biology, for example, how they resist natural defenses and therapeutic intervention. One resistance mechanism involves extracellular vesicles that are released by tumors to meet target cells nearby or distant via circulation and reprogram them by introducing their cargo. This consists of different molecules among which are microRNAs (miRNAs) and molecular chaperones, the focus of this article. miRNAs modify target cells in the immune system to avoid antitumor reaction and chaperones are key survival molecules for the tumor cell. Extracellular vesicles cargo reflects the composition and metabolism of the original tumor cell; therefore, it is a source of markers, including the miRNAs and chaperones discussed in this article, with potential diagnostic and prognostic value. This and their relatively easy availability by minimally invasive procedures (e.g., drawing venous blood) illustrate the potential of extracellular vesicles as useful materials to manage brain tumor patients. Furthermore, understanding extracellular vesicles circulation and interaction with target cells will provide the basis for using this vesicle for delivering therapeutic compounds to selected tumor cells.  
brain tumors; extracellular vesicles; miRNA; molecular chaperones; diagnostic tools; drug delivery 1  
[PERSON]  
such as venous thrombosis, pulmonary embolism, intracranial bleeding, wound and systemic infection, seizures, depression, deteriorating neurologic conditions, and adverse drug reaction [2]. This worrying scenario points to the need for novel methods that will allow earlier and more accurate diagnosis and better patient monitoring and treatment than those currently available.  
Remarkable achievements in the molecular and genetic fields have opened new frontiers in the management of brain tumors, including the identification of new diagnostic and prognostic molecular biomarkers released by the tumor. Noteworthy examples of these biomarkers are carried by extracellular vesicles (EVs), released by tumors. EVs, which are considered mediators of intercellular communication, carry bioactive molecules between cells close by or distant, affecting physiological and pathological processes in recipient cells [3; 4; 5; 6; 7; 8; 9]. MicroRNAs (miRNAs) and molecular chaperones are among the bioactive molecules carried by EVs that affect, either directly or indirectly, cancer initiation, cell proliferation and growth, and metastas [10; 11; 12; 13; 14]. Consequently, specific miRNAs and molecular chaperones have been suggested as targets for analysis that can provide useful information for differential diagnosis, assessing prognosis and response to treatment, and for developing novel therapies [15]. One added advantage is that EVs can be obtained from biological fluids with minimally invasive procedures.  
Here, we discuss the role of EVs in the pathogenesis of brain tumors, summarizing current knowledge regarding their miRNAs and molecular chaperones cargo. We examine their role in the development of brain tumors, and their impact on the tumor microenvironment.