A round lump growing inside the cheek may be caused by lymphadenitis, parotitis, oral mucosal polyps and other reasons. 1. Lymphadenitis: If the patient has a round lump in the cheek, it may be caused by lymphadenitis. Lymphadenitis usually leads to enlargement of the lymph nodes, which may be accompanied by pain in severe cases. 2. Mumps: When a patient feels a lump in the cheek, it may be caused by mumps. Mumps is usually caused by bacterial and viral infections, and its main symptoms are redness, swelling and pain. 3. Oral mucosal polyps: usually a round lump inside the cheeks may also be a mucosal polyp formed by long-term biting, which usually protrudes from the mucosal surface without pain or discomfort. There are many other reasons for the growth of a round lump inside the cheeks, and it is recommended that patients seek timely medical attention to clarify the cause of the disease and then standardized treatment.