TACSTD2 and breast cancer: It is known that cancer cell-specific molecules known as cancer antigens such as EGFR (colorectal cancer), GD2 (neuroblastoma), HER2 (breast cancer), VEGFR2 (gastric cancer), Nectin-4 (bladder cancer), or TROP2 (triple-negative breast cancer) are expressed on the surface of cancer cells (Table 1) [1].