Surroundings of tumors including nearby cells and blood vessels
The tumor microenvironment is a complex ecosystem surrounding a tumor, composed of cancer cells, stromal tissue (including blood vessels, immune cells, fibroblasts and signaling molecules) and the extracellular matrix.[2][3][4][5] Mutual interaction between cancer cells and the different components of the tumor microenvironment support its growth and invasion in healthy tissues which correlates with tumor resistance to current treatments and poor prognosis. The tumor microenvironment is in constant change because of the tumor's ability to influence the microenvironment by releasing extracellular signals, promoting tumor angiogenesis and inducing peripheral immune tolerance, while the immune cells in the microenvironment can affect the growth and evolution of cancerous cells.[2][6][7][8][9]