TACSTD2 and neoplasm: Trophoblastic cell-surface antigen 2 (TROP2) is a transmembrane glycoprotein originally identified as an antigen in trophoblasts of the placenta aiding in implantation.1 More recently, it has been implicated in cancer signaling as well, giving rise to its gene name Tumor-associated calcium signal transducer 2 (TACSTD2).1 TROP2/TACSTD2 is elevated in tumor tissue relative to normal and therefore has gained interest as a cancer-specific drug target, particularly for late-stage disease.2