A 43-year-old patient complains of a tumour in the right submandibular region which appeared two months ago after having flu. Objectively: palpation of the right submandibular region reveals a painful spherical neoplasm of dense elastic consistency with regular outlines which is not attached to the skin. Submandibular salivary gland secretes transparent saliva. Sublingual plica is unchanged. Which disease are these clinical presentations typical for?