A 15-year-old girl consulted a dental surgeon about a moderate swelling of the parotid-masticatory region on the left. Objectively: on palpation, the left parotid gland is nodular, dense, painless. The duct exudes somewhat turbid saliva. The duct mouth is dilated, the surrounding mucous membrane is cyanotic, pasty, with imprints of teeth. Make a diagnosis: