FAS and cancer: In the circulation of cancer patients, the majority of lymphocytes are Fas+ T‐cells and it is clear that the Fas/FasL pathway is directly involved in spontaneous apoptosis of circulating Fas+ T‐cells.148 Apoptosis of tumor‐infiltrating lymphocytes (TILs) found in tumor sites is also related to FasL expression on the surface of tumor cells.149 FAS/FASL‐mediated apoptosis leads to a turnover of T‐lymphocytes in the circulation and at tumor sites and, subsequently, a functional lymphocyte imbalance and reduction of the immune competence in these patients.