TACSTD2 and breast cancer: Other targeted therapies currently used in breast cancer management include the antibody–drug conjugate sacituzumab govitecan in metastatic triple-negative breast cancer (mTNBC [14]) targeting trophoblast cell surface antigen 2 (Trop2) and the phosphoinositide 3-kinases (PI3Ks) inhibitors for patients with ER + tumors with a somatic mutation in PIK3CA [15].