Curious case of submandibular swelling

A 35-year-old woman presented with a progressively increasing swelling over the left side of the upper part of the neck for the past 8 months with no associated pain over the swelling. On examination, a non-tender, firm, well-defined, oval swelling of size 3×2 cm was palpable in the left submandibular region that was mobile, non-pulsatile and free from the overlying skin and the underlying muscle. Ultrasonography revealed a bilobed heteroechoic lesion in the left submandibular region with internal vascularity and multiple macrocalcification within it. During the procedure for surgically excising the swelling, we found that it was separate from the gland and vascular structures, had a sinus tracking over and around the left submandibular gland extending beyond the angle of mandible up to the root of a decayed left lower second molar tooth.