Francien H. van Nederveen

An immunohistochemical procedure to detect patients with paraganglioma and phaeochromocytoma with germline SDHB, SDHC, or SDHD gene mutations: a retrospective and prospective analysis.

BACKGROUND Phaeochromocytomas and paragangliomas are neuro-endocrine tumours that occur sporadically and in several hereditary tumour syndromes, including the phaeochromocytoma-paraganglioma syndrome. This syndrome is caused by germline mutations in succinate dehydrogenase B (SDHB), C (SDHC), or D (SDHD) genes. Clinically, the phaeochromocytoma-paraganglioma syndrome is often unrecognised, although 10-30% of apparently sporadic phaeochromocytomas and paragangliomas harbour germline SDH-gene mutations. Despite these figures, the screening of phaeochromocytomas and paragangliomas for mutations in the SDH genes to detect phaeochromocytoma-paraganglioma syndrome is rarely done because of time and financial constraints. We investigated whether SDHB immunohistochemistry could effectively discriminate between SDH-related and non-SDH-related phaeochromocytomas and paragangliomas in large retrospective and prospective tumour series. METHODS Immunohistochemistry for SDHB was done on 220 tumours. Two retrospective series of 175 phaeochromocytomas and paragangliomas with known germline mutation status for phaeochromocytoma-susceptibility or paraganglioma-susceptibility genes were investigated. Additionally, a prospective series of 45 phaeochromocytomas and paragangliomas was investigated for SDHB immunostaining followed by SDHB, SDHC, and SDHD mutation testing. FINDINGS SDHB protein expression was absent in all 102 phaeochromocytomas and paragangliomas with an SDHB, SDHC, or SDHD mutation, but was present in all 65 paraganglionic tumours related to multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and neurofibromatosis type 1. 47 (89%) of the 53 phaeochromocytomas and paragangliomas with no syndromic germline mutation showed SDHB expression. The sensitivity and specificity of the SDHB immunohistochemistry to detect the presence of an SDH mutation in the prospective series were 100% (95% CI 87-100) and 84% (60-97), respectively. INTERPRETATION Phaeochromocytoma-paraganglioma syndrome can be diagnosed reliably by an immunohistochemical procedure. SDHB, SDHC, and SDHD germline mutation testing is indicated only in patients with SDHB-negative tumours. SDHB immunohistochemistry on phaeochromocytomas and paragangliomas could improve the diagnosis of phaeochromocytoma-paraganglioma syndrome. FUNDING The Netherlands Organisation for Scientific Research, Dutch Cancer Society, Vanderes Foundation, Association pour la Recherche contre le Cancer, Institut National de la Santé et de la Recherche Médicale, and a PHRC grant COMETE 3 for the COMETE network.

SDHA Immunohistochemistry Detects Germline SDHA Gene Mutations in Apparently Sporadic Paragangliomas and Pheochromocytomas

CONTEXT Pheochromocytoma-paraganglioma syndrome is caused by mutations in SDHB, SDHC, and SDHD, encoding subunits of succinate dehydrogenase (SDH), and in SDHAF2, required for flavination of SDHA. A recent report described a patient with an abdominal paraganglioma, immunohistochemically negative for SDHA, and identified a causal germline mutation in SDHA. OBJECTIVE In this study, we evaluated the significance of SDHA immunohistochemistry in the identification of new patients with SDHA mutations. SETTING This study was performed in the Erasmus Medical Center in Rotterdam (The Netherlands) and the Université Paris Descartes in Paris (France). METHODS We investigated 316 pheochromocytomas and paragangliomas for SDHA expression. Sequence analysis of SDHA was performed on all tumors that were immunohistochemically negative for SDHA and on a subset of tumors immunohistochemically positive for SDHA. RESULTS Six tumors were immunohistochemically negative for SDHA. Four tumors from Dutch patients showed a germline c.91C → T SDHA gene mutation (p.Arg31X). Another tumor (from France) carried a germline SDHA missense mutation c.1753C → T (p.Arg585Trp). Loss of the wild-type SDHA allele was confirmed by loss of heterozygosity analysis. Sequence analysis of 35 SDHA immunohistochemically positive tumors did not reveal additional SDHA mutations. CONCLUSIONS Our results demonstrate that SDHA immunohistochemistry on paraffin-embedded tumors can reveal the presence of SDHA germline mutations and allowed the identification of SDHA-related tumors in at least 3% of patients affected by apparently sporadic (para)sympathetic paragangliomas and pheochromocytomas.

SDHB immunohistochemistry: a useful tool in the diagnosis of Carney–Stratakis and Carney triad gastrointestinal stromal tumors

Mutations in the tumor suppressor genes SDHB, SDHC, and SDHD (or collectively SDHx) cause the inherited paraganglioma syndromes, characterized by pheochromocytomas and paragangliomas. However, other tumors have been associated with SDHx mutations, such as gastrointestinal stromal tumors (GISTs) specifically in the context of Carney–Stratakis syndrome. Previously, we have shown that SDHB immunohistochemistry is a reliable technique for the identification of pheochromocytomas and paragangliomas caused by SDHx mutations. We hypothesized that GISTs in patients with SDHx mutations would be negative immunohistochemically for SDHB as well. Four GISTs from patients with Carney–Stratakis syndrome and six from patients with Carney triad were investigated by SDHB immunohistochemistry. Five GISTs with KIT or PDGFRA gene mutations were used as controls. In addition, SDHB immunohistochemistry was performed on 42 apparently sporadic GISTs. In cases in which the SDHB immunohistochemistry was negative, mutational analysis of SDHB, SDHC, and SDHD was performed. All GISTs from patients with Carney–Stratakis syndrome and Carney triad were negative for SDHB immunohistochemically. In one patient with Carney–Stratakis syndrome, a germline SDHB mutation was found (p.Ser92Thr). The five GISTs with a KIT or PDGFRA gene mutation were all immunohistochemically positive for SDHB. Of the 42 sporadic tumors, one GIST was SDHB-negative. Mutational analysis of this tumor did not reveal an SDHx mutation. All SDHB-negative GISTs were located in the stomach, had an epithelioid morphology, and had no KIT or PDGFRA mutations. We show that Carney–Stratakis syndrome- and Carney-triad-associated GISTs are negative by immunohistochemistry for SDHB in contrast to KIT- or PDGFRA-mutated GISTs and a majority of sporadic GISTs. We suggest that GISTs of epithelioid cell morphology are tested for SDHB immunohistochemically. In case of negative SDHB staining in GISTs, Carney–Stratakis syndrome or Carney triad should be considered and appropriate clinical surveillance should be instituted.

Observer Variation in the Application of the Pheochromocytoma of the Adrenal Gland Scaled Score

Morphologic determination of the malignant potential of adrenal pheochromocytoma is a challenging problem in surgical pathology. A multiparameter Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) was recently developed based on a comprehensive study of a single institutional cohort of 100 cases. Assignment of a PASS was proposed to be useful for identifying pheochromocytomas with potential to metastasize, which defines malignancy according to the current World Health Organization terminology. A PASS is derived by evaluating multiple morphologic parameters to obtain a scaled score based on the summed weighted importance of each. Despite the proposal of this system several years ago, few studies have since examined its robustness and, in particular, the potential for observer variation inherent in the interpretation and assessment of these morphologic criteria. We further examined the utility of PASS by reviewing an independent single institutional cohort of adrenal pheochromocytomas as evaluated by 5 multi-institutional pathologists with at least 10 years experience in endocrine pathology. We found significant interobserver and intraobserver variation in assignment of PASS with variable interpretation of the underlying components. We consequently suggest that PASS requires further refinement and validation. We cannot currently recommend its use for clinical prognostication.

Head and Neck Paragangliomas in Von Hippel-Lindau Disease and Multiple Endocrine Neoplasia Type 2

BACKGROUND Head and neck paragangliomas (HNPs) occur as sporadic or familial entities, the latter mostly in association with germline mutations of the SDHB, SDHC, or SDHD (SDHx) genes. Heritable non-SDHx HNP might occur in von Hippel-Lindau disease (VHL, VHL gene), multiple endocrine neoplasia type 2 (MEN2, RET gene), and neurofibromatosis type 1 (NF1, NF1 gene). Reports of non-SDHx HNP presentations are scarce and guidance for genetic testing nonexistent. PATIENTS AND METHODS An international consortium registered patients with HNPs and performed mutation analyses of the SDHx, VHL, and RET genes. Those with SDHx germline mutations were excluded for purposes of this study. Personal and family histories were evaluated for paraganglial tumors, for the major tumor manifestations, and for family history of VHL, MEN2, or NF1. RESULTS Twelve patients were found to have hereditary non-SDHx HNPs of a total of 809 HNP and 2084 VHL registrants, 11 in the setting of germline VHL mutations and one of a RET mutation. The prevalence of hereditary HNP is five in 1000 VHL patients and nine in 1000 non-SDHx HNP patients. Comprehensive literature review revealed previous reports of HNPs in five VHL, two MEN2, and one NF1 patient. Overall, 11 here presented HNP cases, and four previously reported VHL-HNPs had lesions characteristic for VHL and/or a positive family history for VHL. CONCLUSIONS Our observations provide evidence that molecular genetic testing for VHL or RET germline mutations in patients with HNP should be done only if personal and/or family history shows evidence for one of these syndromes.

Non-pheochromocytoma (PCC)/paraganglioma (PGL) tumors in patients with succinate dehydrogenase-related PCC-PGL syndromes: A clinicopathological and molecular analysis

OBJECTIVE Although the succinate dehydrogenase (SDH)-related tumor spectrum has been recently expanded, there are only rare reports of non-pheochromocytoma/paraganglioma tumors in SDHx-mutated patients. Therefore, questions still remain unresolved concerning the aforementioned tumors with regard to their pathogenesis, clinicopathological phenotype, and even causal relatedness to SDHx mutations. Absence of SDHB expression in tumors derived from tissues susceptible to SDH deficiency is not fully elucidated. DESIGN AND METHODS Three unrelated SDHD patients, two with pituitary adenoma (PA) and one with papillary thyroid carcinoma (PTC), and three SDHB patients affected by renal cell carcinomas (RCCs) were identified from four European centers. SDHA/SDHB immunohistochemistry (IHC), SDHx mutation analysis, and loss of heterozygosity analysis of the involved SDHx gene were performed on all tumors. A cohort of 348 tumors of unknown SDHx mutational status, including renal tumors, PTCs, PAs, neuroblastic tumors, seminomas, and adenomatoid tumors, was investigated by SDHB IHC. RESULTS Of the six index patients, all RCCs and one PA displayed SDHB immunonegativity in contrast to the other PA and PTC. All immunonegative tumors demonstrated loss of the WT allele, indicating bi-allelic inactivation of the germline mutated gene. Of 348 tumors, one clear cell RCC exhibited partial loss of SDHB expression. CONCLUSIONS These findings strengthen the etiological association of SDHx genes with pituitary neoplasia and provide evidence against a link between PTC and SDHx mutations. Somatic deletions seem to constitute the second hit in SDHB-related renal neoplasia, while SDHx alterations do not appear to be primary drivers in sporadic tumorigenesis from tissues affected by SDH deficiency.

SDHA mutations in adult and pediatric wild-type gastrointestinal stromal tumors

Most gastrointestinal stromal tumors (GISTs) harbor oncogenic mutations in KIT or platelet-derived growth factor receptor-α. However, a small subset of GISTs lacks such mutations and is termed ‘wild-type GISTs’. Germline mutation in any of the subunits of succinate dehydrogenase (SDH) predisposes individuals to hereditary paragangliomas and pheochromocytomas. However, germline mutations of the genes encoding SDH subunits A, B, C or D (SDHA, SDHB, SDHC or SDHD; collectively SDHx) are also identified in GISTs. SDHA and SDHB immunohistochemistry are reliable techniques to identify pheochromocytomas and paragangliomas with mutations in SDHA, SDHB, SDHC and SDHD. In this study, we investigated if SDHA immunohistochemistry could also identify SDHA-mutated GISTs. Twenty-four adult wild-type GISTs and nine pediatric/adolescent wild-type GISTs were analyzed with SDHB, and where this was negative, then with SDHA immunohistochemistry. If SDHA immunohistochemistry was negative, sequencing analysis of the entire SDHA coding sequence was performed. All nine pediatric/adolescent GISTs and seven adult wild-type GISTs were negative for SDHB immunohistochemistry. One pediatric GIST and three SDHB-immunonegative adult wild-type GISTs were negative for SDHA immunohistochemistry. In all four SDHA-negative GISTs, a germline SDHA c.91C>T transition was found leading to a nonsense p.Arg31X mutation. Our results demonstrate that SDHA immunohistochemistry on GISTs can identify the presence of an SDHA germline mutation. Identifying GISTs with deficient SDH activity warrants additional genetic testing, evaluation and follow-up for inherited disorders and paragangliomas.

SDHB/SDHA immunohistochemistry in pheochromocytomas and paragangliomas: A multicenter interobserver variation analysis using virtual microscopy: A Multinational Study of the European Network for the Study of Adrenal Tumors (ENS@T)

Despite the established role of SDHB/SDHA immunohistochemistry as a valuable tool to identify patients at risk for familial succinate dehydrogenase-related pheochromocytoma/paraganglioma syndromes, the reproducibility of the assessment methods has not as yet been determined. The aim of this study was to investigate interobserver variability among seven expert endocrine pathologists using a web-based virtual microscopy approach in a large multicenter pheochromocytoma/paraganglioma cohort (n=351): (1) 73 SDH mutated, (2) 105 non-SDH mutated, (3) 128 samples without identified SDH-x mutations, and (4) 45 with incomplete SDH molecular genetic analysis. Substantial agreement among all the reviewers was observed either with a two-tiered classification (SDHB κ=0.7338; SDHA κ=0.6707) or a three-tiered classification approach (SDHB κ=0.6543; SDHA κ=0.7516). Consensus was achieved in 315 cases (89.74%) for SDHB immunohistochemistry and in 348 cases (99.15%) for SDHA immunohistochemistry. Among the concordant cases, 62 of 69 (~90%) SDHB-/C-/D-/AF2-mutated cases displayed SDHB immunonegativity and SDHA immunopositivity, 3 of 4 (75%) with SDHA mutations showed loss of SDHA/SDHB protein expression, whereas 98 of 105 (93%) non-SDH-x-mutated counterparts demonstrated retention of SDHA/SDHB protein expression. Two SDHD-mutated extra-adrenal paragangliomas were scored as SDHB immunopositive, whereas 9 of 128 (7%) tumors without identified SDH-x mutations, 6 of 37 (~16%) VHL-mutated, as well as 1 of 21 (~5%) NF1-mutated tumors were evaluated as SDHB immunonegative. Although 14 out of those 16 SDHB-immunonegative cases were nonmetastatic, an overall significant correlation between SDHB immunonegativity and malignancy was observed (P=0.00019). We conclude that SDHB/SDHA immunohistochemistry is a reliable tool to identify patients with SDH-x mutations with an additional value in the assessment of genetic variants of unknown significance. If SDH molecular genetic analysis fails to detect a mutation in SDHB-immunonegative tumor, SDHC promoter methylation and/or VHL/NF1 testing with the use of targeted next-generation sequencing is advisable.

SDHB loss predicts malignancy in pheochromocytomas/sympathethic paragangliomas, but not through hypoxia signalling

Prediction of malignant behaviour of pheochromocytomas/sympathetic paragangliomas (PCCs/PGLs) is very difficult if not impossible on a histopathological basis. In a familial setting, it is well known that succinate dehydrogenase subunit B (SDHB)-associated PCC/PGL very often metastasise. Recently, absence of SDHB expression as measured through immunohistochemistry was shown to be an excellent indicator of the presence of an SDH germline mutation in PCC/PGL. SDHB loss is believed to lead to tumour formation by activation of hypoxia signals. To clarify the potential use of SDHB immunohistochemistry as a marker of malignancy in PCC/PGL and its association with classic hypoxia signalling we examined SDHB, hypoxia inducible factor-1α (Hif-1α) and its targets CA-9 and GLUT-1 expression on protein level using immunohistochemistry on a tissue micro array on a series of familial and sporadic tumours of 115 patients. Survival data was available for 66 patients. SDHB protein expression was lost in the tumour tissue of 12 of 99 patients. Of those 12 patients, 5 had an SDHB germline mutation, in 4 patients no germline mutation was detected and mutational status remained unknown in parts in 3 patients. Loss of SDHB expression was not associated with increased classic hypoxia signalling as detected by Hif-1α, CA-9 or GLUT-1 staining. Loss of SDHB expression was associated with an adverse outcome. The lack of correlation of SDHB loss with classic hypoxia signals argues against the current hypoxia hypothesis in malignant PCC/PGL. We suggest SDHB protein loss as a marker of adverse outcome both in sporadic and in familial PCC/PGL.

Frequent genetic changes in childhood pheochromocytomas.

Abstract:  Pheochromocytomas (PCCs) are rare catecholamine‐producing tumors of the adrenal gland which may also occur elsewhere in the abdomen and are then called paragangliomas. A proportion of PCCs occurs in hereditary cancer syndromes, including multiple endocrine neoplasia Type 2 (MEN2), caused by mutations in the RET proto‐oncogene, von Hippel–Lindau (VHL) disease, caused by VHL gene abnormalities, and the pheochromocytoma–paraganglioma (PCC–PGL) syndrome, caused by mutations in SDHB and SDHD. Since a proportion of PCCs occurs in children we hypothesized that germline mutations in RET, VHL, succinate dehydrogenase subunit B (SDHB), and subunit D (SDHD) occur more frequently in the pediatric age range. From our single‐institution collection of PCCs, we have selected 10 cases that occurred in individuals up to 18 years of age at diagnosis. In these, we have performed mutation analysis on normal and tumor tissues for exons 10, 11, and 16 of RET and for the entire coding sequence of VHL, SDHB, and SDHD. The 10 patients include 7 boys and 3 girls, with an average age of 15.5 years (range 9–18 years). Two patients had germline RET exon 11 mutations (C634R) and 1 patient had an R64P germline mutation in the VHL gene. In the remaining 7 patients there was one patient from a family fulfilling the clinical criteria for VHL disease. All tumors were benign (average follow‐up: 12 years) and were located in the adrenal. From our findings we conclude that (a) a large proportion (40%) of pediatric PCC patients is diagnosed in the context of inherited cancer syndromes, and (b) candidate gene analysis appears to be indicated to detect germline mutations.