Recent progress in the pathologic classification of pheochromocytomas and paragangliomas.

Abstract

Pheochromocytomas and paragangliomas (PPGLs) represent a unique subset of neuroendocrine neoplasms (NENs) characterized by their genetic diversity and potential for catecholamine secretion. Similar to epithelial NENs, all PPGLs are classified as malignant neoplasms that are associated with a variable risk of metastatic spread. PPGLs arise from neuroendocrine cells of the adrenal medulla (intra-adrenal paraganglia) or extra-adrenal paraganglia. Advances over the past two decades have significantly enhanced our understanding of the biological and genetic underpinnings of these neoplasms, resulting in robust genotype-phenotype (e.g., morphology, anatomic distribution, catecholamine profile, biomarker profile, risk of metastasis) correlations that guide diagnosis and prognostication. The 2022 WHO classification of PPGLs emphasizes a shift away from morphology-only diagnostic approaches by ensuring the integration of morphology with functional, structural and pathogenesis-related biomarker studies into routine pathology practice when assessing PPGLs. This paradigm is critical in distinguishing metastatic disease from multifocal primary tumors, particularly in patients with germline mutations - a hallmark of PPGLs, with germline susceptibility observed in at least 40 % of cases. This review provides practicing pathologists with a concise update on modern diagnostic and risk assessment strategies for PPGLs, focusing on the integration of biomarkers, genetic profiling, and morphological features. It also addresses emerging challenges, such as identifying metastatic potential and distinguishing these from synchronous lesions, to improve multidisciplinary care of these patients.