Parents of a 6-year-old child consulted a doctor about a swelling in his right parotid-masseteric region, dry mouth, fever up to 37,7°C. Similar presentations turned up about 6 months ago. Examination revealed a tuberous, slightly painful infiltrate in the right parotid-masseteric region. Saliva is viscous, the right salivary gland duct discharges some secretion with whitish inclusions. What is the most likely diagnosis?