TEM1 (Tumor endothelial marker 1), also named as CD248, Endosialin and CD164L1, is a C-type lectin-like domain (CTLD) containing type I transmembrane glycoprotein. It is now considered to be a highly selective marker for activated perivascular and stromal cells, detected in most cancers and at least some inflammatory disorders. CD248 plays a role in tumor angiogenesis. It is a potential diagnostic tool and therapeutic target of inflammatory and malignant disease. Two isoforms of human TEM1 exist. The calculated molecular weights of the two isoforms are 81 kDa and 46 kDa, respectively. Native TEM1 can be glycosylated, and the glycosylated form has a larger apparent molecular weight than 81 kDa.