Endoscopy and Biopsy 
• A biopsy is necessary for a definitive diagnosis and is most useful for patients with suspected metastatic
  disease. The primary tumor may be biopsied surgically or with a CT- or ultrasound-directed needle biopsy or
  surgically after a metabolic work-up reveals it is not a pheochromocytoma. Biopsies of suspected
  pheochromocytoma must not be undertaken without full catecholamine blockade (see below).
• Alternatively, an accessible metastasis in the lymph nodes or liver can be biopsied.