is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.These contrast with benign tumors, which do not spread.Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements.While these symptoms may indicate cancer, they can also have other causes. Over 100 types of cancers affect humans symptoms: Lump, abnormal bleeding, prolonged cough, unexplained weight loss, change in bowel movements Risk factor: Tobacco, obesity, poor diet, lack of physical activity, excessive alcohol, certain infections Treatment: Radiation therapy, surgery, chemotherapy, and targeted therapy Classification: Carcinoma: Cancers derived from epithelial cells. This group includes many of the most common cancers and include nearly all those in the breast, prostate, lung, pancreas and colon. Sarcoma: Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve), each of which develops from cells originating in mesenchymal cells outside the bone marrow. Lymphoma and leukemia: These two classes arise from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. Germ cell tumor: Cancers derived from pluripotent cells, most often presenting in the testicle or the ovary (seminoma and dysgerminoma, respectively). Blastoma: Cancers derived from immature "precursor" cells or embryonic tissue.