Lesions at the very back of your mouth could be a sign of oral cancer, which is not exactly common, but it is also not rare. The American Cancer Society estimates that 45,780 new cases of oral cavity or pharynx cancer will be diagnosed in 2015, just over half the number of expected skin cancer cases. Cancers at the base of the tongue and tonsils (called oropharyngeal cancers) are most commonly caused by the human papillomavirus infection (HPV).

Although the lesions can show up anywhere in the mouth, yet they are most likely to develop under the tongue around the base and near your esophagus. Oral cavity and oropharyngeal tumors are twice as likely to develop in men as in women, and the American Cancer Society reports a recent uptick in cases of oropharyngeal cancers linked to HPV.