Challenges in Paragangliomas and Pheochromocytomas: from Histology to Molecular Immunohistochemistry

Abdominal paragangliomas and pheochromocytomas (PPGLs) are rare neuroendocrine tumors of the infradiaphragmatic paraganglia and adrenal medulla, respectively. Although few pathologists outside of endocrine tertiary centers will ever diagnose such a lesion, the tumors are well known through the medical community-possible due to a combination of the sheer rarity, their often-spectacular presentation due to excess catecholamine secretion as well as their unrivaled coupling to constitutional susceptibility gene mutations and hereditary syndromes. All PPGLs are thought to harbor malignant potential, and therefore pose several challenges to the practicing pathologist. Specifically, a responsible diagnostician should recognize both the capacity and limitations of histological, immunohistochemical, and molecular algorithms to pinpoint high risk for future metastatic disease. This focused review aims to provide the surgical pathologist with a condensed update regarding the current strategies available in order to deliver an accurate prognostication of these enigmatic lesions.