PDCD6IP and head and neck squamous cell carcinoma: Characteristics of sEV isolated from plasma of HNSCC patients or HDs’ plasma were comparable: all vesicles carried one or more tetraspanins (CD9 CD63, CD81), and all were TSG101-positive and ALIX-positive, indicating their endocytic origin, and did not carry cytoplasmic proteins, calnexin or Grp94.