A 41-year-old man presented with a 1-year history of a slowly expanding right neck mass (Figure 1). During the past few months, he had also developed diffuse bone pain and had recently begun to use a cane to walk. The patient's medical history was significant for end-stage renal disease as a sequela of Wegener granulomatosis; he had been receiving hemodialysis for more than 10 years. Five years ago, the patient underwent neck surgery, although he was unable to provide specific details. Physical examination revealed a transverse Kocher incision and a 2-cm round, mobile mass in the right neck at level III. Laboratory testing revealed hypercalcemia (total calcium level, 11.7 mg/dL; reference range, 8.0-10.4; to convert to millimoles per liter, multiply by 0.025) and elevated parathyroid hormone level (>2500 pg/mL; reference range, 12-65 pg/mL).