TM4SF1 and neoplasm: Each TMED contains 3 to 14 TM4SF1 molecules and TMED increase in number and size when TM4SF1 expression is high, such as in proliferating endothelial cells in vitro7, 8, 11 and in tumor endothelium in vivo8 TMEDs function as membrane docks that recruit a variety of other membrane proteins and their intracellular membrane‐proximal signaling components.8, 11