The main therapeutic strategy used in 75% of all breast cancers targets estrogen receptor α (ERα). However, the mechanisms underlying ERα therapeutic resistance are still elusive hampered by the challenges in developing suitable experimental models. In this work, a novel ex-vivo culture strategy was developed. This strategy is based on tissue microstructures encapsulation in alginate, enabling maintenance of original tissue structure, cell populations and extracellular matrix, thus recapitulating the tumoral microenvironment in which ERα signaling is sustained.