A 43-year-old patient complains of a neoplasm in the right submaxillary area that appeared a month ago after angina. Body temperature is 37, 0 − 37, 2°C. The patient underwent anti-inflammatory therapy but the neoplasm didn’t diminish. Objectively: palpation of the right submaxillary area reveals a slightly painful spherical neoplasm of dense elastic consistency with regular outlines that is not adherent to skin. The duct of submandibular salivary gland excretes transparent saliva. Sublingual torus is unchanged. What is the most probable diagnosis?