Mutation analysis of the SDHD gene in four kindreds with familial paraganglioma: description of one novel germline mutation

Carney triad, SDH-deficient tumors, and Sdhb+/- mice share abnormal mitochondria

Carney triad (CTr) describes the association of paragangliomas (PGL), pulmonary chondromas, and gastrointestinal (GI) stromal tumors (GISTs) with a variety of other lesions, including pheochromocytomas and adrenocortical tumors. The gene(s) that cause CTr remain(s) unknown. PGL and GISTs may be caused by loss-of-function mutations in succinate dehydrogenase (SDH) (a condition known as Carney-Stratakis syndrome (CSS)). Mitochondrial structure and function are abnormal in tissues that carry SDH defects, but they have not been studied in CTr. For the present study, we examined mitochondrial structure in human tumors and GI tissue (GIT) of mice with SDH deficiency. Tissues from 16 CTr tumors (n=12), those with isolated GIST (n=1), and those with CSS caused by SDHC (n=1) and SDHD (n=2) mutations were studied by electron microscopy (EM). Samples of GIT from mice with a heterozygous deletion in Sdhb (Sdhb(+) (/-), n=4) were also studied by EM. CTr patients presented with mostly epithelioid GISTs that were characterized by plump cells containing a centrally located, round nucleus and prominent nucleoli; these changes were almost identical to those seen in the GISTs of patients with SDH. In tumor cells from patients, regardless of diagnosis or tumor type, cytoplasm contained an increased number of mitochondria with a 'hypoxic' phenotype: mitochondria were devoid of cristae, exhibited structural abnormalities, and were of variable size. Occasionally, mitochondria were small and round; rarely, they were thin and elongated with tubular cristae. Many mitochondria exhibited amorphous fluffy material with membranous whorls or cystic structures. A similar mitochondrial hypoxic phenotype was seen in Sdhb(+) (/-) mice. We concluded that tissues from SDH-deficient tumors, those from mouse GIT, and those from CTr tumors shared identical abnormalities in mitochondrial structure and other features. Thus, the still-elusive CTr defect(s) is(are) likely to affect mitochondrial function, just like germline SDH-deficiency does.

Familial cervical paragangliomas with lymph node metastasis expressing somatostatin receptor type 2A

We report a case of familial, bilateral cervical paragangliomas (PGs) with lymph node metastasis. Patient I-1 is a 56-year-old man with a right carotid body tumor and a left vagal PG. Patient II-1 is a 29-year-old woman and the daughter of Patient I-1; she had a left carotid body tumor with regional lymph node metastasis. Histology of all the tumors showed the typical pattern of PGs, i.e., a zellballen pattern composed of chief cells positive for chromogranin A, and sustentacular cells positive for S100 protein. The Ki-67 labeling index was 1% to 3% in these PGs in both the primary and the metastatic tumors. Immunohistochemical analysis showed expression of somatostatin receptor (sstr) type 2A, but was negative for sstr type 5. Genomic mutation in succinate dehydrogenase type D was confirmed in both patients. Here, we present a case of familial PGs, and discuss the cases with special reference to pathologic diagnosis, genetics, and treatment.

SDH mutations in tumorigenesis and inherited endocrine tumours: lesson from the phaeochromocytoma-paraganglioma syndromes

A genetic predisposition for paragangliomas and adrenal or extra-adrenal phaeochromocytomas was recognized years ago. Beside the well-known syndromes associated with an increased risk of adrenal phaeochromocytoma, Von Hippel Lindau disease, multiple endocrine neoplasia type 2 and neurofibromatosis type 1, the study of inherited predisposition to head and neck paragangliomas led to the discovery of the novel 'paraganglioma-phaeochromocytoma syndrome' caused by germline mutations in three genes encoding subunits of the succinate dehydrogenase (SDH) enzyme (SDHB, SDHC and SDHD) thus opening an unexpected connection between mitochondrial tumour suppressor genes and neural crest-derived cancers. Germline mutations in SDH genes are responsible for 6% and 9% of sporadic paragangliomas and phaeochromocytomas, respectively, 29% of paediatric cases, 38% of malignant tumours and more than 80% of familial aggregations of paraganglioma and phaeochromocytoma. The disease is characterized by autosomal dominant inheritance with a peculiar parent-of-origin effect for SDHD mutations. Life-time tumour risk seems higher than 70% with variable clinical manifestantions depending on the mutated gene. In this review we summarize the most recent knowledge about the role of SDH deficiency in tumorigenesis, the spectrum and prevalence of SDH mutations derived from several series of cases, the related clinical manifestantions including rare phenotypes, such as the association of paragangliomas with gastrointestinal stromal tumours and kidney cancers, and the biological hypotheses attempting to explain genotype to phenotype correlation.

Impact of screening kindreds for SDHD p.Cys11X as a common mutation associated with paraganglioma syndrome type 1

CONTEXT AND OBJECTIVE

Germline mutations of the genes SDHB, SDHC, and SDHD predispose to paraganglioma syndromes. Mutation-specific counseling, risk assessment, and management recommendations ideally should be performed. Here, we provide data for a single common mutation of the SDHD gene.

METHODS

The European-American Pheochromocytoma-Paraganglioma Registry served as the source for unrelated index cases affected by pheochromocytoma or paraganglioma. Patients with the SDHD c.33 C-->A (p.Cys11X) germline mutations were reinvestigated by whole-body magnetic resonance imaging and 24-h urinary catecholamine assay. First-degree relatives underwent genetic testing and those testing positive had same clinical investigations. Microsatellite analyses were used to test the hypothesis that all index cases were related and the mutation is a founding one.

RESULTS

Sixteen index cases with the mutation SDHD p.Cys11X are registered. After testing their relatives, there were a total of 25 mutation carriers. We excluded seven subjects who inherited the mutation from the mother because of maternal imprinting. Thus, 18 mutation carriers were clinically affected. Among these 16 (89%) had head and neck paragangliomas, six (33%) thoracic tumors, six (33%) extraadrenal retroperitoneal, and five (28%) intraadrenal. Of note, 16 (89%) had multiple tumors at first diagnosis, and one (5%) had signs of malignancy during follow-up. Overall penetrance was 100% at age 54. Haplotype analyses revealed evidence for a founder effect.

CONCLUSIONS

The SDHD p.Cys11X mutation is a founding mutation associated with a high penetrance for paraganglial tumors of the skull base, neck, thorax, and retroperitoneum in the first four decades of life and, rarely, with malignancy.

Paraganglioma syndrome: SDHB, SDHC, and SDHD mutations in head and neck paragangliomas

Paraganglioma syndrome includes head and neck paraganglioma and pheochromocytoma, and is classified according to the three susceptibility genes involved, SDHB, SDHC, and SDHD. This study assessed the prevalence of germline mutations in SDHB, SDHC, and SDHD genes in a consecutive population admitted to Padova Hospital consisting of 20 patients with head and neck paraganglioma (HNP). Mutations were identified in the three genes in four affected individuals, three sporadic cases and one with family history of HNP. The novel SDHB p.R242C mutation was identified in a sporadic monolateral carotid body tumor. The SDHC p.Q147X mutation, the first to be described in Italy, was detected in a sporadic monolateral jugulotympanic paraganglioma. The SDHD p.Y114C mutation was identified in two unrelated patients, one familial case of bilateral carotid body tumor and one multiple paraganglioma. SDHB, SDHC, and SDHD molecular screening is important in all HNPs, with or without primary indicators of paraganglioma syndrome, to orient mutation-driven clinical screening for additional HNPs and pheochromocytoma.

A novel G106D alteration of theSDHDgene in a pedigree with familial paraganglioma

Head and neck paragangliomas are tumors derived from parasympathetic paraganglia. Familial cases account for 10% or more of these tumors, and mutations of the genes encoding subunits for the mitochondrial respiratory chain complex II, SDHD, SDHB, and SDHC, have been reported. We analyzed mutations in the all four SDH genes, SDHA through SDHD, in a Japanese family with cervical paraganglioma that include a father with bilateral tumors and his daughter with a malignant left carotid body tumor with nodal metastasis. This pedigree harbored a germline G106D alteration in exon 4 of the SDHD gene that has not previously been reported to date. The tumors of the father expressed biallelic SDHD, but the SDHD expression was highly suppressed by an unknown mechanism(s) in tumors of his daughter, and the wild-type allele was predominantly suppressed in the metastatic node. These results suggest that the missense dysfunction of SDHD prepares neoplastic condition and that expressional silencing, particularly of the wild-type allele, plays an important role in the malignant transformation of the paragangliomas. Our results may lead to a better understanding of this disease and to the development of methods for prevention of this disease.