Light micrograph of a section of human pharynx tissue showing oral and oropharyngeal cancer. This is a disease in which malignant (cancerous) cells form in the tissues of the oropharynx. The oropharynx is the portion of the pharynx that is posterior to the oral cavity. It serves both the respiratory and digestive systems and is the most critical region in swallowing. Smoking or being infected with human papillomavirus (HPV) can increase the risk of oropharyngeal cancer. Signs and symptoms include a lump in the neck and a sore throat.