CCL2 and neoplasm: Given that CCL2‐expressing astrocytes mediate the extravasation of T lymphocytes in the brain, and that CCL2 facilitates the process of both migration and infiltration of several cell systems such as monocytes, natural killer cells, T lymphocytes, and memory cells,167 defining how E2 modulates astrocytic CCL2 expression during different stages of metastatic colonization may shed light into the specific contribution of E2 to the transition of a tumor‐suppressive early brain niche to a tumor‐promoting immunosuppressive late brain niche.