Pheochromocytoma classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ahmad Al Maradni, M.D. [2] Mohammed Abdelwahed M.D[3]
Overview
Pheochromocytomas and paragangliomas (collectively referred to as PPGLs) are rare tumors that originate from chromaffin cells in the adrenal medulla (pheochromocytoma) or in the extra-adrenal neural ganglia (paraganglioma). These tumors can be either biochemically active (producing a catecholamine like epinephrine, nor-epinephrine and dopamine) or biochemically silent. PPGLs can be either sporadic or genetic, with association to several familial syndromes. PPGLs can also be classified according to their spread into local, regional, or metastatic. The defining characteristic of malignancy in PPGLs is the presence of metastasis.
Classification
Pheochromocytoma may be classified into several subtypes based on:
- Nature of tumor
- Spread
- Genetics
Classification based on nature of tumor:
Malignant and benign tumors share the same biochemical and histological characters. The only difference is the ability of the malignant tumor to metastasize to distant tissues and have high rates of recurrence.
Classification based on spread:
- Localized:
- 95% of pheochromocytomas are found in the abdomen
- 85 to 90 % are intra-adrenal
- 5 to 10% are multiple
- 15-20% of PPGLs are extra-adrenal (paragangliomas).
- Regional
- Metastatic: common sites of metastasis include:
Classification based on genetics:
Familial pheochromocytoma
- Familial pheochromocytoma is associated with several hereditary disorders including Multiple Endocrine Neoplasia types 2A and 2B (MEN2) (caused by mutations of the RET gene), Von Hippel-Lindau (VHL) disease (caused by mutations of the VHL gene), familial paraganglioma of the neck (cause by mutations of the gene for succinate dehydrogenase subunit D (SDHD)) and neurofibromatosis type 1 (NF1).
Non-familial pheochromocytoma:
- Resulting from sporadic germ-line mutations, which have been documented in about 20% of cases.
- The majority of them are positive for KIT expression, some are not. A partial explanation was provided by the finding of activating mutations in another gene encoding an RTK, the platelet-derived growth factor receptor alpha (PDGFRA) gene in some KIT-negative GISTs:
Sporadic:
- Most catecholamine-secreting tumors are sporadic. Mutations have been identified in most of the sporadic cases.
- May be due to spontaneous mutation, decreased penetrance or maternal imprinting.[1]
- 50% of patients had a pathogenic mutation in SDHB, SDHD, or VHL.[2]
References
- ↑ Buffet A, Venisse A, Nau V, Roncellin I, Boccio V, Le Pottier N; et al. (2012). "A decade (2001-2010) of genetic testing for pheochromocytoma and paraganglioma". Horm Metab Res. 44 (5): 359–66. doi:10.1055/s-0032-1304594. PMID 22517557.
- ↑ Jafri M, Whitworth J, Rattenberry E, Vialard L, Kilby G, Kumar AV; et al. (2013). "Evaluation of SDHB, SDHD and VHL gene susceptibility testing in the assessment of individuals with non-syndromic phaeochromocytoma, paraganglioma and head and neck paraganglioma". Clin Endocrinol (Oxf). 78 (6): 898–906. doi:10.1111/cen.12074. PMID 23072324.