Background/Objectives: Sacituzumab govitecan (SG) is an antibody–drug conjugate targeting Trop-2 that has demonstrated clinical benefits in randomised trials for patients with metastatic triple-negative breast cancer (mTNBC) and metastatic hormone receptor-positive/HER2-negative (HR+/HER2− mBC) disease. The gene discussed is TACSTD2; the disease is triple-negative breast carcinoma.