CAROTID-BODY TUMOR MIMICKING ADENOCARCINOMA ON FINE-NEEDLE ASPIRATION

We report an 86-year-old woman who presented with a 6-month history of a mass in the left side of her neck. MRI and MRI angiography favored a diagnosis of a neural tumor. FNAB showed a large cluster of cohesive , pleomorphic cells with intranuclear inclusion bodies; a diagnosis of adenocarcinoma was favored. At surgery, a 7 x 5 x 2.5 cm, firm, encap sulated mass was excised. Microscopically, the richly vascularized tum or had characteristics of a CBT, with large pleomorphic chief cells an d spindle-shaped sustentacular cells in small, poorly formed nests. Th e chief cells were strongly immunoreactive for neuron-specific enolase and chromogranin, and focally positive for neurofilament, enkephalin, somatostatin, and beta-endorphin. The sustentacular cells were strong ly immunoreactive for S-100 protein and glial fibrillary acidic protei n and focally positive for vimentin. Ultrastructurally, the chief cell s contained abundant neurosecretory granules. We emphasize that CBT mu st be included in the differential diagnosis of lateral neck masses. T he distinction from adenocarcinoma is difficult on FNAB. The marked cy tological atypia in an aspirate of a COT does not indicate malignancy and may lead to an erroneous diagnosis.