A 41-year-old man presented with a 7-month history of episodes of back and abdominal pain associated with nausea, vomiting, and flushing. Immediately following workup with noncontrast abdominal ultrasonography, he experienced intense flushing and vomiting. Subsequent contrast-enhanced magnetic resonance imaging identified a 5-cm thoracic paraspinal mass (Figure, A). Computed tomography–guided biopsy of the paraspinal mass revealed a dense cellular infiltrate on histopathology composed of cells with round nuclei and abundant pale cytoplasm (Figure, B).