A 60-year-old man complains of stabbing pain near the root of the tongue on the right, which develops during eating, especially sour food. Objectively: there is a swelling in the right submandibular area. On palpation the submandibular gland is dense and enlarged. Excretory duct orifice of the right submandibular gland is dilated and produces mucopurulent secretion. What is the most likely diagnosis?