Germline mutations in PTEN and SDHC in a woman with epithelial thyroid cancer and carotid paraganglioma

Metastatic Malignant Paraganglioma Presenting as a Neck Mass Treated with Radiolabeled Somatostatin Analog

Paragangliomas are rare neuroendocrine tumors that arise from chromaffin-containing tissue. Surgical resection and/or radiation are used for locoregional disease, and reduction of tumor burden with systemic therapy is reserved for metastatic disease. Iobenguane I-131, somatostatin analog (octreotide), and Sunitinib are noncytotoxic options for treatment, while cyclophosphamide, vincristine, and dacarbazine (CVD) and temozolomide are often used as initial chemotherapy options as studies have shown that they offer some tumor response. However, there are no randomized clinical trials demonstrating prolonged survival with the use of chemotherapeutics in metastatic cases. Investigation of alternative therapies that provide survival benefit is thus necessary. We present a case of a 69-year-old female with metastatic malignant paraganglioma presenting as a left parapharyngeal neck mass, which metastasized after surgery, requiring radiation therapy for bony metastasis who was treated with a radioisotope somatostatin analog for disease progression.

What Have We Learned from Molecular Biology of Paragangliomas and Pheochromocytomas?

Recent advances in molecular genetics and genomics have led to increased understanding of the aetiopathogenesis of pheochromocytomas and paragangliomas (PPGLs). Thus, pan-genomic studies now provide a comprehensive integrated genomic analysis of PPGLs into distinct molecularly defined subtypes concordant with tumour genotypes. In addition, new embryological discoveries have refined the concept of how normal paraganglia develop, potentially establishing a developmental basis for genotype-phenotype correlations for PPGLs. The challenge for modern pathology is to translate these scientific discoveries into routine practice, which will be based largely on histopathology for the foreseeable future. Here, we review recent progress concerning the cell of origin and molecular pathogenesis of PPGLs, including pathogenetic mechanisms, genetic susceptibility and molecular classification. The current roles and tools of pathologists are considered from a histopathological perspective, including differential diagnoses, genotype-phenotype correlations and the use of immunohistochemistry in identifying hereditary predisposition and validating genetic variants of unknown significance. Current and potential molecular prognosticators are also presented with the hope that predictive molecular biomarkers will be integrated into risk stratification scoring systems to assess the metastatic potential of these intriguing neoplasms and identify potential drug targets.

"Mitochondrial Toolbox" - A Review of Online Resources to Explore Mitochondrial Genomics

Mitochondria play a significant role in many biological systems. There is emerging evidence that differences in the mitochondrial genome may contribute to multiple common diseases, leading to an increasing number of studies exploring mitochondrial genomics. There is often a large amount of complex data generated (for example via next generation sequencing), which requires optimised bioinformatics tools to efficiently and effectively generate robust outcomes from these large datasets. Twenty-four online resources dedicated to mitochondrial genomics were reviewed. This 'mitochondrial toolbox' summary resource will enable researchers to rapidly identify the resource(s) most suitable for their needs. These resources fulfil a variety of functions, with some being highly specialised. No single tool will provide all users with the resources they require; therefore, the most suitable tool will vary between users depending on the nature of the work they aim to carry out. Genetics resources are well established for phylogeny and DNA sequence changes, but further epigenetic and gene expression resources need to be developed for mitochondrial genomics.

Cardiac Paraganglioma in a 14-Year-Old

Cardiac paraganglioma (PGL) is a rare catecholamine-secreting tumor forming 1% to 3% of cardiac tumors. Although most PGL occur sporadically, evidence exists that 40% of them may be related to familial cancer predisposition syndromes. We present a unique case of a 14-year-old female who presented with persistent hypertension and was found to have a cardiac PGL. During surgical resection, even though the main right coronary was preserved, the sinoatrial (SA) nodal artery was surrounded by the tumor and required resection with the tumor. The patient subsequently developed SA node dysfunction and is currently being evaluated for placement of a permanent pacemaker.

Concomitant paraganglioma and thyroid carcinoma: A case report

BACKGROUND

Paraganglioma/pheochromocytoma and medullary thyroid carcinoma can coexist and are often found in multiple endocrine neoplasia (MEN). However, very few cases highlight papillary thyroid carcinoma. We present herein a rare case of head and neck paraganglioma associated with papillary thyroid carcinoma.

CASE SUMMARY

A 51-year-old man presented to our department with right-sided neck swelling and hypertension. Physical examination showed neck masses with obvious pulsation. Concentrations of serum calcium, phosphorus, parathormone, thyroid stimulating hormone, free thyroxine, and calcitonin were within normal limits. Enhanced computed tomography revealed an irregular solid nodule, located in the carotid artery bifurcation. A low-density nodule of the thyroid isthmus with a spot-like dense shadow was also detected. The diagnosis of carotid body tumor was raised and an ultrasound-guided fine needle aspiration biopsy of the thyroid nodule revealed papillary thyroid carcinoma. The patient underwent surgery for lesion excision, total thyroidectomy, and neck dissection, and the pathology was reported as paraganglioma and papillary carcinoma. Genetic studies showed negative results for germline mutation of succinate dehydrogenase subunit D on 11q23. He was treated with ¹³¹I after surgery and remained disease-free so far.

CONCLUSION

The presence of concomitant paraganglioma and thyroid papillary carcinoma could be either coincidental or a result of an unknown mutation.

HABP2 p.G534E variant in patients with family history of thyroid and breast cancer

Familial Papillary Thyroid Carcinoma (PTC) has been described as a hereditary predisposition cancer syndrome associated with mutations in candidate genes including HABP2. Two of 20 probands from families with history of PTC and breast carcinoma (BC) were evaluated by whole exome sequencing (WES) revealing HABP2 p.G534E. Sanger sequencing was used to confirm the involvement of this variant in three families (F1: 7 relatives; F2: 3 and F3: 3). The proband and his sister (with no malignant tumor so far) from F1 were homozygous for the variant whereas one relative with PTC from F2 was negative for the variant. Although the proband of the F3 with PTC was HABP2 wild type, three relatives presented the variant. Five of 170 healthy Brazilian individuals with no family history of BC or PTC and three of 50 sporadic PTC presented the p.G534E. These findings suggested no association of this variant with our familial PTC cases. Genes potentially associated with deregulation of the extracellular matrix organization pathway (CTSB, TNXB, COL4A3, COL16A1, COL24A1, COL5A2, NID1, LOXL2, MMP11, TRIM24 and MUSK) and DNA repair function (NBN and MSH2) were detected by WES, suggesting that other cancer-associated genes have pathogenic effects in the risk of familial PTC development.

PRECISION MEDICINE: AN UPDATE ON GENOTYPE/BIOCHEMICAL PHENOTYPE RELATIONSHIPS IN PHEOCHROMOCYTOMA/PARAGANGLIOMA PATIENTS

OBJECTIVE

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors known to produce and secrete high levels of circulating catecholamines and their metabolites. The biochemical characteristics of these tumors can be used to divide them into three major phenotypes. The adrenergic, noradrenergic and dopaminergic phenotypes are defined by predominant elevations in epinephrine and metanephrine, norepinephrine and normetanephrine, and dopamine and 3-methoxytyramine, respectively. There are over 15 well-identified tumor-susceptibility genes responsible for approximately 40% of the cases. The objective of this review article is to outline specific genotype/biochemical phenotype relationships.

METHODS

Literature review.

RESULTS

None.

CONCLUSION

Biochemical phenotype of PPGL is determined by the underlying genetic mutation and the associated molecular pathway. Identification of genotype/biochemical relationships is valuable in prioritizing testing for specific genes, making treatment decisions and monitoring disease progression.

ABBREVIATIONS

3-MT = 3-methoxytyramine; EPAS1 = endothelial pas domain protein 1; FH = fumarate hydratase; HIF2A = hypoxia inducible factor type 2A; MEN2 = multiple endocrine neoplasia type 2; NF1 = neurofibromatosis type 1; PNMT = phenylethanolamine N-methyltransferase; PPGL = pheochromocytoma and paraganglioma; RET = rearranged during transfection; SDH = succinate dehydrogenase; SDHAF2 = succinate dehydrogenase complex assembly factor 2; TCA = tricarboxylic acid; TH = tyrosine hydroxylase; TMEM127 = transmembrane protein 127; VHL = von Hippel-Lindau.

A SDHC Founder Mutation Causes Paragangliomas (PGLs) in the French Canadians: New Insights on the SDHC-Related PGL

BACKGROUND

More than 40% of patients with paragangliomas (PGLs) harbor a germline mutation of the known PGL susceptibility genes, mainly in the SDHB or SDHD genes.

OBJECTIVE

The objective of the study was to characterize the genetic background of the French Canadian (FC) patients with PGLs and provide new clinical and paraclinical insights on SDHC-related PGLs.

METHODS

Genetic testing has been offered to FC patients affected with PGLs followed up at the adrenal genetics clinic at Centre hospitalier de l'Université de Montréal. After genetic counseling, 29 FC patients consented for PGL genetic testing.

RESULTS

Thirteen of 29 patients (44.8%) carried a germline mutation. The same heterozygous nonsense mutation at codon 133 of exon 5 of the SDHC gene (c.397C>T, p.[Arg133Ter]) was found in nine patients, representing 69.2% of the patients having a germline mutation. Seventy percent of these patients had head and neck PGLs. Twenty percent had multiple and 30% had malignant PGLs. We traced back the ascending genealogy of 10 index cases (nine patients from our cohort and one patient referred to us) and found that this mutation was most probably introduced in Nouvelle France by a couple of French settlers who established themselves in the 17th century.

CONCLUSIONS

We found that 31% of the PGLs in the French Canadian can be explained by the SDHC mutation (c.397C>T, p.[Arg133Ter]). The dominance of the SDHC mutation is unique to the FCs and is most likely due to a French founder effect. SDHC gene analysis should be prioritized in FC patients with PGL.

Coexistence of paraganglioma/pheochromocytoma and papillary thyroid carcinoma: a four-case series analysis

The paraganglioma (PGL)/pheochromocytoma (PHEO)-papillary thyroid carcinoma (PTC) dyad has been reported rarely. Whether the association is coincidental or results from an underlying genetic predisposition is difficult to ascertain. We analyzed clinical and molecular data on four unrelated patients identified and treated by one of us (MJB) at a tertiary center. Patients were screened for germline variants in a panel of candidate genes: RET, VHL, SDHB, SDHC, SDHD, SDHAF2, TMEM127, MAX, PTEN, CDKN1B. All patients were female; median age at diagnosis of PGL/PHEO was 45 years and at diagnosis of PTC was 49.5 years. Only one patient had family history of thyroid cancer. PTC was multifocal in 2 cases, of the classical type in 2 cases and of the follicular type in 2 cases. Two patients harbored heterozygous germline variants of uncertain significance in the SDHB gene: Ser163Pro and Ala3Gly. The -79T>C polymorphism in the CDKN1B gene was present in all patients (3 in homozygous and 1 in heterozygous state). Results deriving from a comprehensive analysis of a panel of genes suggest that there is no single explanation for the association PGL/PHEO-PTC. It may occur through different mechanisms such as the combinatorial effect of different genetic variants, be a coincidental association or, alternatively, result from genetic variants in genes still awaiting identification.

Familiar Papillary Thyroid Carcinoma in a Large Brazilian Family Is Not Associated with Succinate Dehydrogenase Defects

BACKGROUND

Thyroid cancer is the most common endocrine gland malignancy. Advances in understanding the genetic basis for thyroid cancer revealed the potential involvement of several genes in the formation of thyroid tumors. Mutations in the gene coding for succinate dehydrogenase subtype B (SDHB) have been implicated in papillary thyroid cancer (PTC). Succinate dehydrogenase (SDH) is a heterotetrameric protein composed of four subunits, SDHA, SDHB, SDHC, and SDHD, and participates in both the electron transport chain and the tricarboxylic acid cycle. The aim of the study was to evaluate the association between variants in the SDHA, SDHB, SDHC, and SDHD genes and familiar PTC in a large Brazilian family.

METHOD

Four patients with PTC, 1 patient with PTC and gastrointestinal stromal tumor (GIST), 1 patient with GIST, and their relatives - several of them with different thyroid problems - from a large Brazilian family were screened for genetic variations of SDHx genes with the use of polymerase chain reaction-single-stranded conformational polymorphism and direct sequencing.

RESULTS

Only one rare variation in SDHA was found in some of the family members, but not segregating with the disease. No other genetic variants of these genes were detected in the family members that presented with PTC and/or GIST.

CONCLUSION

Familiar PTC and a GIST were not associated with SDHx mutations; additional genetic defects, yet unknown, may be responsible for the development of tumor.

AN AGGRESSIVE TEMPORAL BONE SDHC PARAGANGLIOMA ASSOCIATED WITH INCREASED HIF-2α SIGNALING

OBJECTIVE

To describe a patient with a germline succinate dehydrogenase (SDHC) gene mutation presenting with primary hyperparathyroidism and a large catecholamine-producing temporal bone paraganglioma (PGL).

METHODS

Evaluation of a SDHC mutation-positive PGL tumor biology using staining for tyrosine hydroxylase (TH), hypoxia-inducible factors 1α (HIF-1α) and 2α (HIF-2α).

RESULTS

A 66-year-old man was noted to have a lytic skull base mass during work-up for his primary hyperparathyroidism. Biochemical evaluation with 24-hour urine catecholamines and metanephrines revealed marked elevation of norepinephrine and normetanephrine. Genetic testing revealed a germline SDHC mutation. A partial excision of skull base tumor was performed, which upon further examination revealed PGL. Immunohistochemistry of skull base PGL demonstrated heavy expression of TH and HIF-2α but reduced expression of HIF-1α. The remaining skull base PGL was treated with adjuvant radiation therapy. The patient's normetanephrine levels significantly decreased after surgery and radiation.

CONCLUSION

Here, we report an unusual case of a patient presenting with a germline SDHC mutation-related functional PGL along with concomitant primary hyperparathyroidism. The present case illustrates that overexpression of HIF-2α but not of HIF-1α is linked to the pathogenesis of SDHC mutation-related PGL, and it may be responsible for the aggressive clinical behavior of a usually indolent course of SDHC-related PGLs.

Elevation of methylated DNA in KILLIN/PTEN in the plasma of patients with thyroid and/or breast cancer

Around 80% of mutations in the PTEN gene have been reported to be associated with diseases such as Cowden syndrome, which is an autosomal dominant disorder associated with an increased risk of developing breast, thyroid, and endometrial neoplasms. Recent studies have also demonstrated that KILLIN, which is located proximally to PTEN, shares the same transcription start site, and is assumed to be regulated by the same promoter, but is transcribed in the opposite direction. In this regard, we postulate that there may be a connection between KILLIN/PTEN genes and breast and thyroid cancers. Using real-time quantitative polymerase chain reaction (qPCR), we found that expression of KILLIN, but not PTEN, was significantly decreased in 23 Chinese women with a personal history of breast and thyroid cancer or a personal history of breast cancer and a family history of thyroid cancer, or vice versa, and at least two persons in the family with thyroid cancer or at a young age <40 years, when compared with healthy controls (P<0.0001). No PTEN mutations were found in these 23 patients. We then developed a simple methylation-sensitive restriction enzyme digestion followed by real-time quantitative assay to quantify plasma methylated KILLIN/PTEN DNA in these patients. Plasma levels of methylated KILLIN/PTEN DNA were significantly increased in these patients when compared with healthy controls (P<0.05). This study shows that plasma methylated KILLIN/PTEN DNA was significantly elevated, suggesting hypermethylation of the KILLIN/PTEN promoter in breast and thyroid cancer patients.

The clinical phenotype of SDHC-associated hereditary paraganglioma syndrome (PGL3)

CONTEXT

Mutations in the genes encoding subunits of the succinate dehydrogenase complex cause hereditary paraganglioma syndromes. Although the phenotypes associated with the more commonly mutated genes, SDHB and SDHD, are well described, less is known about SDHC-associated paragangliomas.

OBJECTIVE

To describe functionality, penetrance, number of primary tumors, biological behavior, and location of paragangliomas associated with SDHC mutations.

DESIGN

Families with an SDHC mutation were identified through a large cancer genetics registry. A retrospective chart review was conducted with a focus on patient and tumor characteristics. In addition, clinical reports on SDHC-related paragangliomas were identified in the medical literature to further define the phenotype and compare findings.

SETTING

A cancer genetics clinic and registry at a tertiary referral center.

PATIENTS

Eight index patients with SDHC-related paraganglioma were identified.

RESULTS

Three of the eight index patients had mediastinal paraganglioma and four of the eight patients had more than one paraganglioma. Interestingly, the index patients were the only affected individuals in all families. When combining these index cases with reported cases in the medical literature, the mediastinum is the second most common location for SDHC-related paraganglioma (10% of all tumors), occurring in up to 13% of patients.

CONCLUSIONS

Our findings suggest that thoracic paragangliomas are common in patients with SDHC mutations, and imaging of this area should be included in surveillance of mutation carriers. In addition, the absence of paragangliomas among at-risk relatives of SDHC mutation carriers suggests a less penetrant phenotype as compared to SDHB and SDHD mutations.

Phenotypic variability and risk of malignancy in SDHC-linked paragangliomas: lessons from three unrelated cases with an identical germline mutation (p.Arg133*)

CONTEXT

Mutations in the four subunits of succinate dehydrogenase (SDH) are the cause for the hereditary paraganglioma (PGL) syndrome types 1-4 and are associated with multiple and recurrent pheochromocytomas and PGLs. SDHC mutations most frequently result in benign, nonfunctional head-and neck PGLs (HNPGLs). The malignant potential of SDHC mutations remains unclear to date.

OBJECTIVES

We report a patient with malignant PGL carrying a SDHC mutation and compare her case with two others of the same genotype but presenting with classic benign HNPGLs. Loss of heterozygosity (LOH) was demonstrated in the malignant PGL tissue.

DESIGN

In three unrelated patients referred for routine genetic testing, SDHB, SDHC, and SDHD genes were sequenced, and gross deletions were excluded by multiplex ligation-dependent probe amplification (MLPA). LOH was determined by pyrosequencing-based allele quantification and SDHB immunohistochemistry.

RESULTS

In a patient with a nonfunctioning thoracic PGL metastatic to the bone, the lungs, and mediastinal lymph nodes, we detected the SDHC mutation c.397C>T predicting a truncated protein due to a premature stop codon (p.Arg133*). We demonstrated LOH and loss of SDHB protein expression in the malignant tumor tissue. The two other patients also carried c.397C>T, p.Arg133*; they differed from each other with respect to their tumor characteristics, but both showed benign HNPGLs.

CONCLUSIONS

We describe the first case of a malignant PGL with distant metastases caused by a SDHC germline mutation. The present case shows that SDHC germline mutations can have highly variable phenotypes and may cause malignant PGL, although malignancy is probably rare.

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.

Genetics of pheochromocytoma and paraganglioma syndromes: new advances and future treatment options

PURPOSE OF REVIEW

To summarize the recent advances in the genetics of pheochromocytoma and paraganglioma (PHEO/PGL), focusing on the new susceptibility genes and dividing PHEOs/PGLs into two groups based on their transcription profile.

RECENT FINDINGS

Recently, TMEM127, MYC-associated factor X, and hypoxia-inducible factor (HIF) 2α have been described in the pathogenesis of PHEOs/PGLs. Thus, now about 30-40% of these tumors are linked to the germline mutations, which also include mutations in the VHL, RET, NF1, SDHx, and SDHAF2 genes. Furthermore, PHEOs/PGLs have been divided into two groups, cluster 1 (SDHx/VHL) and cluster 2 (RET/NF1), based on the transcription profile revealed by genome-wide expression microarray analysis.

SUMMARY

PHEOs/PGLs are the most inherited tumors among (neuro)endocrine tumors. Future approaches in genetics, including whole-genome sequencing, will allow the discovery of additional PHEO/PGL susceptibility genes. The current division of PHEOs/PGLs into cluster 1 and 2 provides us with additional knowledge related to the pathogenesis of these tumors, including the introduction of new treatment options for patients with metastatic PHEOs/PGLs. New discoveries related to the role of the HIF-1/HIF-2α genes in the pathogenesis of almost all inherited PHEOs/PGLs may call for a new regrouping of these tumors and discoveries of new treatment targets.

Succinate dehydrogenase kidney cancer: an aggressive example of the Warburg effect in cancer

PURPOSE

Recently, a new renal cell cancer syndrome has been linked to germline mutation of multiple subunits (SDHB/C/D) of the Krebs cycle enzyme, succinate dehydrogenase. We report our experience with the diagnosis, evaluation and treatment of this novel form of hereditary kidney cancer.

MATERIALS AND METHODS

Patients with suspected hereditary kidney cancer were enrolled on a National Cancer Institute institutional review board approved protocol to study inherited forms of kidney cancer. Individuals from families with germline SDHB, SDHC and SDHD mutations, and kidney cancer underwent comprehensive clinical and genetic evaluation.

RESULTS

A total of 14 patients from 12 SDHB mutation families were evaluated. Patients presented with renal cell cancer at an early age (33 years, range 15 to 62), metastatic kidney cancer developed in 4 and some families had no manifestation other than kidney tumors. An additional family with 6 individuals found to have clear cell renal cell cancer that presented at a young average age (47 years, range 40 to 53) was identified with a germline SDHC mutation (R133X) Metastatic disease developed in 2 of these family members. A patient with a history of carotid body paragangliomas and an aggressive form of kidney cancer was evaluated from a family with a germline SDHD mutation.

CONCLUSIONS

SDH mutation associated renal cell carcinoma can be an aggressive type of kidney cancer, especially in younger individuals. Although detection and management of early tumors is most often associated with a good outcome, based on our initial experience with these patients and our long-term experience with hereditary leiomyomatosis and renal cell carcinoma, we recommend careful surveillance of patients at risk for SDH mutation associated renal cell carcinoma and wide surgical excision of renal tumors.

Model animals for the study of oxidative stress from complex II

Mitochondria play a role of energy production and produce intracellular reactive oxygen species (ROS), especially superoxide anion (O2(-)) as a byproduct of energy metabolism at the same time. O2(-) is converted from oxygen and is overproduced by excessive electron leakage from the mitochondrial respiratory chain. It is well known that mitochondrial complexes I and III in the electron transport system are the major endogenous ROS sources. We have previously demonstrated that mutations in complex II can result in excessive ROS (specifically in SDHC: G71E in Caenorhabditis elegans, I71E in Drosophila and V69E in mouse). Moreover, this results in premature death in C. elegans and Drosophila as well as tumorigenesis in mouse embryonic fibroblast cells. In humans, it has been reported that mutations in SDHB, SDHC or SDHD, which are the subunits of mitochondrial complex II, often result in inherited head and neck paragangliomas (PGLs). Recently, we established Tet-mev-1 conditional transgenic mice using our uniquely developed Tet-On/Off system, which can induce the mutated SDHC gene to be equally and competitively expressed compared to the endogenous wild-type SDHC gene. These mice experienced mitochondrial respiratory chain dysfunction that resulted in oxidative stress. The mitochondrial oxidative stress caused excessive apoptosis in several tissues leading to low-birth-weight infants and growth retardation during neonatal developmental phase in Tet-mev-1 mice. Tet-mev-1 mice also displayed precocious age-dependent corneal physiological changes, delayed corneal epithelialization, decreased corneal endothelial cells, thickened Descemet's membrane and thinning of parenchyma with corneal pathological dysfunctions such as keratitis, Fuchs' corneal dystrophy (FCD) and probably keratoconus after the normal development and growth phase. Here, we review the relationships between mitochondrial oxidative stress and phenomena in mev-1 animal models with mitochondrial complex II SDHC mutations. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.

Clustering of sebaceous gland carcinoma, papillary thyroid carcinoma and breast cancer in a woman as a new cancer susceptibility disorder: a case report

Introduction

Multiple distinct tumors arising in a single individual or within members of a family raise the suspicion of a genetic susceptibility disorder.

Case presentation

We present the case of a 52-year-old Caucasian woman diagnosed with sebaceous gland carcinoma of the eyelid, followed several years later with subsequent diagnoses of breast cancer and papillary carcinoma of the thyroid. Although the patient was also exposed to radiation from a pipe used in the oil field industry, the constellation of neoplasms in this patient suggests the manifestation of a known hereditary susceptibility cancer syndrome. However, testing for the most likely candidates such as Muir-Torre and Cowden syndrome proved negative.

Conclusion

We propose that our patient's clustering of neoplasms either represents a novel cancer susceptibility disorder, of which sebaceous gland carcinoma is a characteristic feature, or is a variant of the Muir-Torre syndrome.

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.