An 8-year-old boy is referred to your office with a 10-day history of a new onset midline neck mass. The mass started as a small lump, but quickly increased in size and became red. It is not painful. He has no sore throat, dysphagia, or fever. On physical examination, you find a 1.5 cm mass in the midline, above the level of the thyroid cartilage that is erythematous, soft, non-tender, and does not move with tongue protrusion. The patient is afebrile. The remainder of the head and neck exam is unremarkable. The appearance of the mass is shown in Figure 4.1.