Small EVs from astrocytes mediated the transfer of miRNA-19a targeting PTEN into metastatic breast cancer cells, resulting in a lack of PTEN expression and increased secretion of the cytokine chemokine (C-C motif) ligand 2 (CCL2) as well as recruitment of IBA1-expressing positive myeloid cells to the metastatic site. Here, PTEN is linked to breast carcinoma.