A 56-year-old woman has noticed an enlarging lump on the right side of her neck for the past 7 months. On physical examination, there is a 3-cm nodule in the right upper neck, medial to the sternocleidomastoid muscle and lateral to the trachea at the angle of the mandible. CT scan shows a circumscribed, solid mass adjacent to the carotid bifurcation. Microscopic examination of the excised mass shows nests of round cells with pink, granular cytoplasm. Tests for immunohistochemical markers chromogranin and S-100 are positive. Electron microscopy shows neurosecretory granules in the tumor cell cytoplasm. The tumor recurs 1 year later and is again excised. What is the most likely diagnosis?