Here is a 44-year-old male asymptomatic with a chance finding of a well defined round opacity 9 mm in diameter.
It has a circular layered appearance and is located probably at the posterior edge of the mylohyoid muscle where the submandibular duct curls around the muscle.
The differential diagnosis could include a lymph node (but which are often lobulated) and a phlebolith (which usually has a more lucent central vessel lumen).
