Cancer is characterized by uncontrolled cell growth that results in the formation of tumors. Symptoms vary depending on the cancer location but may include lumps, changes in moles or skin, or swollen lymph nodes. Cancers are classified into five main groups including carcinomas, sarcomas, lymphomas, leukemias, and adenomas. Imaging tests are used to detect tumors and determine cancer stage for diagnosis. Risk factors include tobacco smoke, workplace chemicals, diet, lifestyle factors, and radiation exposure.