ESR1 and triple-negative breast carcinoma: Similarly, in 3D-cultured MDA-MB-231 spheroids—an aggressive triple-negative breast cancer (TNBC) model lacking ER, PR, and HER2 receptors—albumin-encapsulated liposomes reduced spheroid viability by more than 50% at equivalent drug doses, outperforming conventional Abraxane® by sustaining drug release within the hypoxic core and overcoming multidrug resistance mechanisms.