TROP2, also known as tumor-associated calcium signal transducer 2 (TACSTD2), is another druggable membrane glycoprotein which is closely related to EpCAM and has also been shown to occur in many epithelial tumors but not in malignant mesotheliomas (summarized in [19,21]). This evidence concerns the gene TACSTD2 and malignant mesothelioma.