Regarding its role in tumor genesis, IL-21 has been proven to induce cytotoxic reactions against tumors such as melanoma [199,200] and has been proven to be produced by Hodgkin’s lymphoma (HL) cancer cells (in contrast to what is known in the unaffected healthy human body), making it considered as a possible biomarker [201]. The gene discussed is IL21; the disease is Hodgkins lymphoma.