Abstract
Pheochromocytoma (PCC) and sympathetic paraganglioma (PGL) are rare neuroendocrine tumors characterized by catecholamine production in the adrenal medulla and extra-adrenal paraganglia. PCC and PGL (PPGL) with metastasis was termed malignant PPGL. However, the distinction between “benign” and “malignant” PPGLs has been debated. Currently, all PPGLs are believed to have some metastatic potential and are assigned malignant tumors (ICD-O/3) by the WHO Classification of Endocrine Organs (2017, 4th edition). Therefore, the previous categories benign and malignant PPGL have been eliminated in favor of risk stratification approach. The Grading of Adrenal Pheochromocytoma and Paraganglioma (GAPP) is a tool for risk stratification for predicting metastasis and the prognosis of patients. At least 30% of PPGLs are hereditary, with 20 genes identified and genotype-phenotype correlations clarified. Of these genes, VHL, RET and NF1 have been well investigated and are the primary cause of bilateral PCC. In addition, mutation of succinate dehydrogenase gene subunits SDHB and SDHD are strongly correlated with extra-adrenal location, younger age, multiple tumors, metastasis and poor prognosis. Disease stratification by catecholamine phenotype and molecular profiling correlates with histological grading by GAPP. PPGLs should be understood comprehensively based on clinical, biochemical, molecular and pathological data for patient care. A flow chart for pathological diagnosis is included.
Highlights
Pheochromocytoma (PCC) and paraganglioma (PGL) are rare neuroendocrine tumors that arise in the adrenal medulla and the extra-adrenal paraganglia, respectively
Recent research on PCC and PGL (PPGL) shows remarkable progress and comprehensive study of clinical, molecular, biochemical and pathological investigations revealed some of the complicated problems associated with PPGLs
Cluster stratification and Grading of Adrenal Pheochromocytoma and Paraganglioma (GAPP) intimately correlate which means genotype and phenotype correlation becomes clear in hereditary PPGLs
Summary
Pheochromocytoma (PCC) and paraganglioma (PGL) are rare neuroendocrine tumors that arise in the adrenal medulla and the extra-adrenal paraganglia, respectively. It was concluded from these results that the diagnosis of benign is not correct for PPGLs with no metastasis at the time of the initial operation and long-term follow up is necessary for patients with PPGL even though the pathologic diagnosis is benign Based on such clinical data, the WHO Endocrine Tumor Classification 4th edition (2017) [1,2] [decided on a New Concept that all PPGLs have some metastatic potential and assigned an International Classification of Diseases for Oncology (ICD-O)-3 (malignant tumors) for all PPGLs, eliminating the previous categories of benign and malignant tumors in favor of an approach based on risk stratification [1,2]. Risk stratification is required to tailor the follow-up protocol after complete resection of PPGLs [12]
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