SPARC and esophageal cancer: Esophageal cancer TME is a very dynamic and complex ecosystem entailing cellular components (cancer-associated fibroblasts (CAFs), immune cells, endothelial cells, pericytes, adipocytes), extracellular matrix proteins (collagen, elastin fibers, fibronectins, proteoglycans, hyaluronic acid, osteopontin, periostin, and SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin or BM-40) and secretory proteins including cytokines, chemokines and many growth factors secreted by tumor and stromal cells.