Tonsils serve as the front lines of the body’s immune system. Also known as “palatine tonsils,” they help the body recognize and defend itself against germs. About 3.5 percent of all oral cancers develop in the tonsils or the oropharynx—the back part of the throat—according to the National Cancer Institute’s Surveillance, Epidemiology and End Results database. Tobacco use is a leading cause of tonsil cancer. Human Papilloma Virus (HPV) is another major cause of one form of tonsil cancer, called squamous cell carcinoma. About 9,000 people a year are diagnosed with HPV-related cancer of the mouth and throat, according to the U.S. Centers for Disease Control and Prevention. Because the tonsils are part of the lymph system, some lymphomas may develop there first.