Human TROP-2, also called tumor associated calcium signal transducer 2 (TACSTD2), gp50 and T16, is a type I cell surface glycoprotein that is highly expressed on human carcinomas. It is related to EpCAM, also called TROP-1, gp40 and KSA. A study of these two genes suggests that TROP-2 was generated through the retropositioning of the EpCAM gene. TROP-2 and EpCAM share approximately 49% amino acid sequence identity and approximately 67% similarity. Mature human and mouse TROP-2 share 80% amino acid identity.