Summary
We report a comprehensive molecular characterization of pheochromocytomas
and paragangliomas (PCC/PGLs), a rare tumor type. Multi-platform integration
revealed that PCC/PGLs are driven by diverse alterations affecting multiple
genes and pathways. Pathogenic germline mutations occurred in eight PCC/PGL
susceptibility genes. We identified CSDE1 as a
somatically-mutated driver gene, complementing four known drivers
(HRAS, RET, EPAS1,
NF1). We also discovered fusion genes in PCC/PGL, involving
MAML3, BRAF, NGFR and
NF1. Integrated analysis classified PCC/PGLs into four
molecularly-defined groups: a kinase signaling subtype, a pseudohypoxia subtype,
a Wnt-altered subtype, driven by MAML3 and
CSDE1, and a cortical admixture subtype. Correlates of
metastatic PCC/PGL included the MAML3 fusion gene. This
integrated molecular characterization provides a comprehensive foundation for
developing PCC/PGL precision medicine.
Significant differences between patients with and without PPGL. c Symptom score: one point for each sign: BMI < 25 kg/m 2 , heart rate !85 beats/min, pallor, sweating, palpitations, tremor and nausea; a negative point for obesity.
(18)F-FDA PET/CT is the preferred technique for the localization of the primary PGL and to rule out metastases. Second best, equal alternatives are (18)F-DOPA PET and (123)I-MIBG scintigraphy. For patients with known metastatic PGL, we recommend (18)F-FDA PET in patients with an unknown genotype, (18)F-FDG or (18)F-FDA PET in SDHB mutation carriers, and (18)F-DOPA or (18)F-FDA PET in non-SDHB patients.
SDHB-related PGL often presents as apparently sporadic PGL with symptoms related to tumor mass effect rather than to catecholamine excess. The predominant biochemical phenotype consists of hypersecretion of norepinephrine and/or dopamine, whereas 10% of tumors are biochemically silent. The clinical expression of these tumors cannot be predicted by the genotype.
Purpose: Pheochromocytomas (PCC) and paragangliomas (PGL) are genetically heterogeneous neural crest-derived neoplasms. Recently we identified germline mutations in a new tumor suppressor susceptibility gene, MAX (MYC-associated factor X), which predisposes carriers to PCC. How MAX mutations contribute to PCC/PGL and associated phenotypes remain unclear. This study aimed to examine the prevalence and associated phenotypic features of germline and somatic MAX mutations in PCC/PGL.Design: We sequenced MAX in 1,694 patients with PCC or PGL (without mutations in other major susceptibility genes) from 17 independent referral centers. We screened for large deletions/duplications in 1,535 patients using a multiplex PCR-based method. Somatic mutations were searched for in tumors from an additional 245 patients. The frequency and type of MAX mutation was assessed overall and by clinical characteristics.Results: Sixteen MAX pathogenic mutations were identified in 23 index patients. All had adrenal tumors, including 13 bilateral or multiple PCCs within the same gland (P < 0.001), 15.8% developed additional tumors at thoracoabdominal sites, and 37% had familial antecedents. Age at diagnosis was lower (P ¼ 0.001) in MAX mutation carriers compared with nonmutated cases. Two patients (10.5%) developed metastatic disease. A mutation affecting MAX was found in five tumors, four of them confirmed as somatic (1.65%). MAX tumors were characterized by substantial increases in normetanephrine, associated with normal or minor increases in metanephrine.Conclusions: Germline mutations in MAX are responsible for 1.12% of PCC/PGL in patients without evidence of other known mutations and should be considered in the genetic work-up of these patients.
Summary
Background
There are currently no reliable biomarkers for malignant pheochromocytomas and paragangliomas (PPGLs). This study examined whether measurements of catecholamines and their metabolites might offer utility for this purpose.
Methods
Subjects included 365 patients with PPGLs, including 105 with metastases, and a reference population of 846 without the tumor. Eighteen catecholamine-related analytes were examined in relation to tumor location, size and mutations of succinate dehydrogenase subunit B (SDHB).
Results
Receiver-operating characteristic curves indicated that plasma methoxytyramine, the O-methylated metabolite of dopamine, provided the most accurate biomarker for discriminating patients with and without metastases. Plasma methoxytyramine was 4.7-fold higher in patients with than without metastases, a difference independent of tumor burden and the associated 1.6- to 1.8-fold higher concentrations of norepinephrine and normetanephrine. Increased plasma methoxytyramine was associated with SDHB mutations and extra-adrenal disease, but was also present in patients without SDHB mutations and metastases or those with metastases secondary to adrenal tumors. High risk of malignancy associated with SDHB mutations reflected large size and extra-adrenal locations of tumors, both independent predictors of metastatic disease. A plasma methoxytyramine above 0.2 nmol/L or a tumor diameter above 5 cm indicated increased likelihood of metastatic spread, particularly when associated with an extra-adrenal location.
Interpretation
Plasma methoxytyramine is a novel biomarker for metastatic PPGLs that together with SDHB mutation status, tumor size and location provide useful information to assess the likelihood of malignancy and manage affected patients.
With a sensitivity approaching 100%, [18F]FDG-PET is the preferred functional imaging modality for staging and treatment monitoring of SDHB-related metastatic PGL.
BACKGROUND
Pheochromocytomas are rare catecholamine–producing tumors derived in at least 30% of cases from mutations in 9 tumor-susceptibility genes identified to date. Testing of multiple genes at considerable expense is often undertaken before a mutation is detected. This study assessed whether measurements of plasma metanephrine, normetanephrine and methoxytyramine, the O-methylated metabolites of catecholamines, might help distinguish different hereditary forms of the tumor.
METHODS
Plasma concentrations of O-methylated metabolites were measured by liquid chromatography with electrochemical detection in 173 patients with pheochromocytoma, including 38 with multiple endocrine neoplasia type 2 (MEN 2), 10 with neurofibromatosis type 1 (NF1), 66 with von Hippel-Lindau (VHL) syndrome and 59 with mutations of succinate dehydrogenase (SDH) type B or D genes.
RESULTS
In contrast to patients with VHL and SDH mutations, all patients with MEN 2 and NF1 presented with tumors characterized by increased plasma concentrations of metanephrine (indicating epinephrine production). VHL patients usually showed solitary increases in normetanephrine (indicating norepinephrine production), whereas additional or solitary increases in methoxytyramine (indicating dopamine production) characterized 70% of patients with SDH mutations. Patients with NF1 and MEN 2 could be discriminated from those with VHL and SDH mutations in 99% of cases by the combination of normetanephrine and metanephrine. Measurements of plasma methoxytyramine discriminated patients with SDH mutations from those with VHL mutations in a further 78% of cases.
CONCLUSIONS
The distinct patterns of plasma catecholamine O-methylated metabolites in patients with hereditary pheochromocytoma provide an easily utilized tool to guide cost-effective genotyping of underlying disease-causing mutations.
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