Antiestrogenic adjuvant treatments are first-line therapies in patients with breast cancer positive for estrogen receptor (ER+). Improvement of their treatment strategies is needed because most patients eventually acquire endocrine resistance and many others are initially refractory to anti-estrogen treatments. The tumor microenvironment plays essential roles in cancer development and progress; however, the molecular mechanisms underlying such effects remain poorly understood. Breast cancer cell lines co-cultured with TNF-α conditioned macrophages were used as pro-inflammatory tumor microenvironment models. In our simulated pro-inflammatory tumor microenvironment, Tumor Associated Macrophages (TAMs) promoted proliferation, migration, invasiveness, and breast tumor growth of ER+ cells, rendering these estrogen-dependent breast cancer cells resistant to estrogen withdrawal and tamoxifen or ICI treatment. We proposed that extracellular vesicles (EVs) are one of the most important players in cellular communication and they could be one of the responsible of the endocrine resistance we had observed. Isolation and characterization of EVs is the first step to analyze the content of the vesicles in our cells of interest for further functional assays that will allow us to determine whether they are involved in the communication between TAMs and tumoral cells, and if EVs are responsible of the endocrine resistance that some ER+ cancers acquired with endocrine treatments.