CD326, also known as EpCAM （epithelial cell adhesion molecule） or TACSTD1 （tumor-associated calcium signal transducer 1）, is a 40 kDa type I transmembrane glycoprotein that serves as a calcium-independent homophilic cell adhesion molecule in the basolateral membranes of most epithelial cells. It plays a crucial role in cell adhesion, proliferation, and differentiation, and is highly expressed in various normal epithelial tissues, such as the gastrointestinal tract and liver. However, its expression is significantly upregulated in many epithelial cancers, including colorectal, breast, and prostate cancers, making it a valuable tumor marker. In cancer biology, CD326 is involved in tumor progression, metastasis, and the maintenance of cancer stem cells. It also has potential therapeutic applications, such as targeted drug delivery and immunotherapy, due to its specific expression on cancer cells.