Which histologic findings are characteristic of pheochromocytomas?

Updated: Aug 10, 2018
  • Author: Michael A Blake, MBBCh, MRCPI, FRCR; Chief Editor: George T Griffing, MD  more...
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Pheochromocytomas vary from 2 g to 3 kg but, on average, weigh 100 g (a healthy adrenal gland weighs 4-6 g). These tumors are well encapsulated, highly vascular, and appear reddish brown on cut section.

Histologically, the tumor cells are arranged in balls and clusters separated by endothelium-lined spaces; this classic pattern characteristic of pheochromocytoma is termed zellballen. The cells vary in size and shape and have finely granular basophilic or eosinophilic cytoplasm. The nuclei are round or oval with prominent nucleoli. Nuclear gigantism and hyperchromasia are common and do not portend prognosis.

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