Trophoblast cell-surface antigen 2 (TROP2), also known as tumor-associated calcium signal transducer 2 (TACSTD2), is a cell surface glycoprotein that plays a role in cell signaling, proliferation, and survival. TROP2 is expressed at low levels in normal tissues but is overexpressed in a variety of cancers, including breast, lung, colorectal, pancreatic, and prostate cancers. This overexpression makes TROP2 a valuable target in cancer therapy, particularly for ADCs. TROP2 is commonly overexpressed in many epithelial cancers, where it is associated with aggressive tumor behavior, including enhanced proliferation, invasion, and metastasis. High TROP2 expression often correlates with poor prognosis. TROP2 can activate signaling pathways that promote cancer cell growth and survival, such as the PI3K/AKT and ERK/MAPK pathways.