Trophoblast cell-surface antigen 2 (TROP2), also known as tumor-associated calcium signal transducer 2 (TACSTD2), is a transmembrane glycoprotein with high homology to the epithelial cell. TROP2 was discovered first in trophoblast cells as a surface marker. Gene TACSTD2 located on chromosome 1p32 encodes TROP2. TROP2 consists of extracellular and transmembrane domains and a cytoplasmic tail. TROP2 undergoes intramembrane proteolysis and is cleaved into a large extracellular fragment and a short intracellular fragment. TROP2 increases intracellular calcium concentration, decreases fibronectin binding and cell adhesion, and increases cell motility. TROP2 is overexpressed in several carcinomas, such as colorectal, pancreatic, gastric, oral squamous cell carcinoma, ovarian, and breast cancers, compared with the corresponding normal tissue. Because TROP2 overexpression is associated with poor survival in patients with solid tumors, TROP2 has been considered a potential target for anticancer therapy. In studies of breast and lung cancers, TROP2 inhibition exerted anticancer effects.