The most consistent evidence demonstrates increased risks of: (i) CRC among those with colonic involvement, varying with the extent, severity, and duration of colonic inflammation; (ii) small bowel cancer among those with Crohn’s disease; (iii) lymphoma and non-melanoma skin cancer among those treated with thiopurine medications; and (iv) to some extent, melanoma among those treated with anti Tumor Necrosis Factor (anti-TNF) biologic therapy. This evidence concerns the gene TNF and non-melanoma skin carcinoma.