TSPAN4 is enriched on migrasomes and can be used as a marker protein for migrasomes [4]. Neural crest cells (NCCs) can normally produce migrasomes without TSPAN overexpression [15]. Tetraspanins, also called transmembrane 4 superfamily (TM4SF) proteins, have four highly hydrophobic transmembrane domains [16]. There are currently 33 tetraspanins that are found in humans [17]. Tetraspanins play a role in physiological activities such as cell adhesion, activation, motility, and proliferation, and participate in pathological processes such as viral infection or metastasis [18,19]. Among tumor cells, TSPAN8 is involved in proliferation, metastasis, angiogenesis, and thrombosis [20,21]. CD151 plays a role in the regulation of integrin-dependent cell morphology and cell migration [22]. CD53 and CD37, which interact with immunoreceptors, are only expressed on immune cells [23]. By observing NRK epithelial cell lines that are stably expressing different levels of TSPAN4 and cell lines knocking out TSPAN4, it was confirmed that the expression of TSPAN4 promotes the generation of migrants, and the lack of TSPAN4 will reduce the generation of migrants in the cells [24]. Tetraspanin proteins and cholesterol form Tetraspanin-enriched microdomains (TEMs) on the membranes [17]. Studies have confirmed that the migrasomal membrane is not only rich in TSPAN4 and cholesterol, but also contains integrins and other transmembrane proteins. These micron-scale macrodomains are named TEMAs. Migrasomes are formed due to the presence of TEMAs that swell into large vesicular migrasomal shapes. An in vitro membrane system was designed to simulate the formation of RFs and migrasomes. They are giant unilamellar vesicles (GUVs) containing purified TSPAN4, cholesterol, and other lipids. The results show that GUVs containing TSPAN4 and cholesterol can form migrasome-like structures, while GUVs without cholesterol or TSPAN4 cannot form a migrasome-like structure. Another device also obtained the same result. To explain the physical mechanism of migrasome formation, Professor Yu’s research group and Professor Kozlov’s research group collaborated to establish a theoretical model [24]. The results confirmed that TSPAN4 protein and cholesterol were locally enriched on RFs due to cell migration, which increased the bending rigidity of TEMAs, thereby forming migrasome-like structures [24]. Migrasomes contain CD63 [7]. They were observed in NCCs expressing low levels of pCMV-CD63-pHluorin (CD63-pH) and were stained with BODIPY ceramide. The results showed that RFs were particularly enriched in CD63-pH and migrasomes were brightly labeled with BODIPY ceramide. This suggests that BODIPY ceramide could serve as a migrasome marker [15]. TSPAN4 has pan-cancer significance in most cancer types according to bioinformatics analysis [25]. The expression of TSPAN4 in gastric cancer tissues was significantly higher than that in paracancerous tissues. The downregulation of TSPAN4 in tumor xenografts was able to suppress tumor formation, suggesting that this gene may have a retarding effect on gastric cancer progression [26]. TSPAN4 is highly expressed in lung adenocarcinoma (LUAD) and promotes the metastasis of LUAD [27]. Therefore, TSPAN4 may be a biomarker and a potential therapeutic target for some cancers.