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.

Losses of chromosomes 1p and 3q are early genetic events in the development of sporadic pheochromocytomas

Despite several loss of heterozygosity studies, a comprehensive genomic survey of pheochromocytomas is still lacking. To identify DNA copy number changes which might be important in tumor development and progression and which may have diagnostic utility, we evaluated genetic aberrations in 29 sporadic adrenal and extra-adrenal pheochromocytomas (19 clinically benign tumors and 10 malignant lesions). Comparative genomic hybridization was performed using directly fluorochrome-conjugated DNA extracted from frozen (16) and paraffin-embedded (13) tumor tissues. The most frequently observed changes were losses of chromosomes 1p11-p32 (86%), 3q (52%), 6q (34%), 3p, 17p (31% each), 11q (28%), and gains of chromosomes 9q (38%) and 17q (31%). No amplification was identified and no difference between adrenal and extra-adrenal tumors was detected. Progression to malignant tumors was strongly associated with deletions of chromosome 6q (60% versus 21% in clinically benign lesions, P = 0.0368) and 17p (50% versus 21%). Fluorescence in situ hybridization confirmed the comparative genomic hybridization data of chromosomes 1p, 3q, and 6q, and revealed aneuploidy in some tumors. Our results suggest that the development of pheochromocytomas is associated with specific genomic aberrations, such as losses of 1p, 3q, and 6q and gains of 9q and 17q. In particular, tumor suppressor genes on chromosomes 1p and 3q may be involved in early tumorigenesis, and deletions of chromosomes 6q and 17p in progression to malignancy.

Microarray-based CGH of sporadic and syndrome-related pheochromocytomas using a 0.1-0.2 Mb bacterial artificial chromosome array spanning chromosome arm 1p

Pheochromocytomas (PCC) are relatively rare neuroendocrine tumors, mainly of the adrenal medulla. They arise sporadically or occur secondary to inherited cancer syndromes, such as multiple endocrine neoplasia type II (MEN2), von Hippel-Lindau disease (VHL), or neurofibromatosis type I (NF1). Loss of 1p is the most frequently encountered genetic alteration, especially in MEN2-related and sporadic PCC. Previous studies have revealed three regions of common somatic loss on chromosome arm 1p, using chromosome-based comparative genomic hybridization (CGH) and LOH analysis. To investigate these chromosomal aberrations with a higher resolution and sensitivity, we performed microarray-based CGH with 13 sporadic and 11 syndrome-related (10 MEN2A-related and 1 NF1-related) tumors. The array consisted of 642 overlapping bacterial artificial chromosome (BAC) clones mapped to 1p11.2-p36.33. Chromosomal deletions on 1p were detected in 18 of 24 cases (75%). Among 9 tumors with partial 1p loss, the deleted region was restricted to 1cen-1p32.3 in six cases (25%), indicating a region of genetic instability. The consensus regions of deletion in this study involved 1cen-1p21.1, 1p21.3-1p31.3, and 1p34.3-1p36.33. In conclusion, these data strongly suggest that chromosome arm 1p is the site for multiple tumor suppressor genes, although the potential candidate genes CDKN2C and PTPRF/LAR are not included in these regions.

Frequent loss of 17p, but no p53 mutations or protein overexpression in benign and malignant pheochromocytomas

Genetic changes in the tumorigenesis of sporadic pheochromocytomas are poorly understood, and there are no good markers to discriminate benign from malignant pheochromocytomas. p53 is a tumor suppressor gene and aberrations in this gene are frequently found in many tumor types. The role of p53 in pheochromocytoma tumorigenesis is unclear, with some studies suggesting that p53 mutations can be used to discriminate benign from malignant pheochromocytomas while other studies do not find such an association. Because most of these investigations were hampered by small series of tumors and the use of varying methods, we have performed a comprehensive analysis of p53 aberrations in a large series of pheochromocytomas. Comparative genomic hybridization analysis of 31 benign and 20 malignant tumors showed loss of the p53 locus at chromosome 17p13.1 in 23/51 (45%) cases, and most of these results were confirmed by fluorescence in situ hybridization. Forty-three tumors, including the malignant tumors and the tumors with loss of the p53 locus, were analyzed for p53 mutations in exons 5-8, but none were found. Furthermore, p53 immunohistochemistry on 35 cases revealed strong nuclear p53 expression in only two pheochromocytoma metastases, all other tumors being negative. We conclude that, although there is frequent loss of the p53 locus on 17p, the p53 gene does not appear to play a major role in pheochromocytoma tumorigenesis.

Genetic analyses of apparently sporadic pheochromocytomas: the Rotterdam experience

Pheochromocytomas (PCCs) are neuroendocrine tumors of chromaffin tissue that produce catecholamines. They are usually located in the adrenal medulla, although in about 10% the tumors arise from extra-adrenal chromaffin tissue. The majority of PCCs arise sporadically, but PCCs occur also in the context of hereditary cancer syndromes. Familial PCC is inherited as an autosomal dominant trait alone or as a component of the multiple endocrine neoplasia Type 2 (MEN2) syndrome (RET gene), Von Hippel-Lindau (VHL) disease (VHL gene), neurofibromatosis Type 1 (NF1 gene), or familial pheochromocytoma-paraganglioma (PCC-PGL) syndrome (SDHD/B and C genes). It has been reported that 24% of apparently sporadic PCCs patients harbor germline mutations in these PCC-causing genes. We investigated the contribution of the inherited PCC-causing genes in a partly retrospectively and partly prospectively obtained series of 213 apparently sporadic PCCs. Mutation analysis was performed for RET (56 cases), VHL (136 cases), and SDHD (126 cases) and SDHB (47 cases). No germline RET mutations, six (4.4%) germline VHL mutations, two (1.5%) germline SDHD mutations, and one germline (1.6%) SDHB mutation were found. In total we found germline mutations in about 7.5% of the investigated apparently sporadic PCCs. Although 7.5% germline mutations in a series of apparently sporadic PCCs are far less than the more than 20% reported in the literature, the figure is significant enough to consider germline mutation testing for each patient with PCC.

Differential loss of chromosome 11q in familial and sporadic parasympathetic paragangliomas detected by comparative genomic hybridization

Parasympathetic paragangliomas (PGLs) represent neuroendocrine tumors arising from chief cells in branchiomeric and intravagal paraganglia, which share several histological features with their sympathetic counterpart sympathoadrenal paragangliomas. In recent years, genetic analyses of the familial form of PGL have attracted considerable interest. However, the majority of paragangliomas occurs sporadically and it remains to be determined whether the pathogenesis of sporadic paraganglioma resembles that of the familial form. Furthermore, data on comparative genetic aberrations are scarce. To provide fundamental cytogenetic data on sporadic and hereditary PGLs, we performed comparative genomic hybridization using directly fluorochrome-conjugated DNA extracted from 12 frozen and 4 paraffin-embedded tumors. The comparative genomic hybridization data were extended by loss of heterozygosity analysis of chromosome 11q. DNA copy number changes were found in 10 (63%) of 16 tumors. The most frequent chromosomal imbalance involved loss of chromosome 11. Six of seven familial tumors and two of nine sporadic tumors showed loss of 11q (86% versus 22%, P = 0.012). Deletions of 11p and 5p were found in two of nine sporadic tumors. We conclude that overall DNA copy number changes are infrequent in PGLs compared to sympathetic paragangliomas and that loss of chromosome 11 may be an important event in their tumorigenesis, particularly in familial paragangliomas.

Von Hippel-Lindau gene alterations in sporadic benign and malignant pheochromocytomas

The Von Hippel-Lindau (VHL) gene product has a wide spectrum of tissue-specific functions, and specific germline mutations are associated with clinical phenotypes in VHL disease. In particular, missense mutations are correlated with the susceptibility to pheochromocytomas. An association between VHL aberrations and prognosis has been suggested in renal clear cell carcinoma but has not been studied in pheochromocytomas. We studied the frequency and spectrum of VHL alterations in apparently sporadic pheochromocytomas in relation to the clinical behavior in 72 patients, including 48 patients with clinically benign and 24 patients with malignant pheochromocytomas. Single-strand conformation polymorphism (SSCP) analysis followed by DNA sequencing, loss of heterozygosity analysis of the VHL locus and immunohistochemistry for VHL protein expression were used to investigate somatic VHL gene alterations. In 2 patients, 1 with a malignant tumor, germline mutations were identified in the stop codon. Tumor-specific intragenic VHL mutations and accompanying loss of heterozygosity were identified in 2 (4.3%) of 47 sporadic benign pheochromocytomas compared to 4 (17.4%) of 23 malignant tumors (p = 0.064). Only one of these mutations has been previously described, in a renal clear cell carcinoma. Expression of the VHL protein was observed in all pheochromocytomas. No distinction in the nature of VHL alterations between benign and malignant pheochromocytomas and no correlation with histopathologic or clinical features was observed. We report novel VHL mutations in sporadic pheochromocytomas, which are slightly correlated with malignancy. VHL mutations may have some impact on the malignant transformation of pheochromocytomas.

Molecular genetic alterations in adrenal and extra-adrenal pheochromocytomas and paragangliomas

Pheochromocytomas and paragangliomas are neuroendocrine neoplasias of neural crest origin. Genetic mutations that are characterized in other human neoplasms are rarely seen in these tumors. About 10% of the patients with pheochromocytomas and paragangliomas present with a family history of von Hippel-Lindau disease (VHL), Multiple endocrine neoplasia type 2 (MEN2), one of the three familial paraganglioma syndromes (PGL; PGL1, PGL3, PGL4), or neurofibromatosis type 1 (NF1). In an even higher percentage, a genetic predisposition is involved in the development of these tumors. The genes of hereditary tumor syndromes such as the aforementioned ones are also ideal to study the molecular pathogenesis in the sporadic counterparts. Many studies have been undertaken to identify important secondary genetic events that contribute to the tumorigenesis of pheochromocytoma or paraganglioma, but a comprehensive review of these data is lacking. Recent findings of CGH and LOH studies provided new starting points to unravel the pathogenesis and progression of these tumors. This review presents an overview of our current understanding of the molecular pathogenesis of pheochromocytoma and paraganglioma.

PTEN gene loss, but not mutation, in benign and malignant phaeochromocytomas

Mutations of the 'phosphatase and tensin homologue deleted on chromosome 10' (PTEN/MMAC1) gene have been associated with a variety of human cancers, including prostate cancer, glioblastoma, and melanoma. The gene is thought to be one of the most frequently mutated tumour suppressor genes and inactivation of PTEN is associated with disease progression and angiogenesis. High vascularization and resistance to chemo- and radio-therapy are two well-established features of phaeochromocytomas (PCCs). Furthermore, benign and malignant PCCs are found in several PTEN knockout mouse models. This study therefore evaluated whether inactivation of PTEN may be involved in the tumourigenesis of PCC in man and whether PTEN abnormalities may help to define the malignant potential of these tumours. Tumour and germline DNA was analysed from 31 patients with apparently sporadic PCC, including 14 clinically benign and 17 malignant tumours, for loss of the PTEN gene locus, mutations in the PTEN gene, and for PTEN protein expression by immunohistochemistry. Loss of heterozygosity (LOH) analysis showed loss of PTEN in four malignant tumours (40%) and in one benign tumour (14%). However, no mutations of PTEN were observed. Immunohistochemistry showed no correlation with clinical behaviour and/or LOH status. The results indicate that inactivation of the PTEN/MMAC1 gene may play a minor role in the development of malignant phaeochromocytomas.

Clinical Characteristics of Pheochromocytoma Patients With Germline Mutations in SDHD

Purpose

We examined the value of SDHD mutation screening in patients presenting with apparently sporadic and familial pheochromocytoma for the identification of SDHD-related pheochromocytomas.

Patients and Methods

This retrospective study involved 126 patients with adrenal or extra-adrenal pheochromocytomas, including 24 patients with a family history of multiple endocrine neoplasia 2, von Hippel-Lindau disease, neurofibromatosis type 1, or paraganglioma (PGL). Conformation-dependent gel electrophoresis and sequence determination analysis of germline and tumor DNA were used to identify SDHD alterations. The clinical and molecular characteristics of sporadic and hereditary tumors were compared. We reviewed the literature and compared our results with those from previously published studies.

Results

Pathogenic germline SDHD mutations were identified in three patients: two (2.0%) of the 102 apparently sporadic pheochromocytoma patients and one patient with a family history of PGL. These patients presented with multifocal disease (two of three multifocal patients) or with a single adrenal tumor (one of 82 patients). In the literature, mutations are mostly found in patients ≤ 35 years of age or presenting with multifocal or extra-adrenal disease. All patients with an SDHD mutation developed extra-adrenal tumors (pheochromocytomas or PGLs) at presentation or during follow-up.

Conclusion

SDHD gene mutations in patients presenting with apparently sporadic adrenal pheochromocytoma are rare. We recommend SDHD mutation screening for patients presenting with a family history of pheochromocytoma or PGL, multiple tumors, isolated adrenal or extra-adrenal pheochromocytomas, and age ≤ 35 years. Analysis of SDHD can also help to distinguish synchronous primary tumors from abdominal metastases.

Cutaneous leiomyosarcoma arising in a smallpox scar

BACKGROUND

Cutaneous leiomyosarcoma (CLM) is a very rare smooth muscle tumour that accounts for about 2-3% of all superficial soft tissue sarcomas. Although the development of various malignancies in scar tissue is well known, we report the first case of a CLM developing in a small pox scar.

CASE PRESENTATION

A 66-year-old man presented with a painless, slow-growing lump in a small pox scar on his left shoulder. Histological biopsies showed the lesion to be a primary, well-differentiated cutaneous leiomyosarcoma. A CT scan of the thorax was conducted, which showed no signs of metastases. The complete lesion was then surgically excised, and histopathological examination revealed a radically excised cutaneous type leiomyosarcoma After 13 months' review the patient was doing well with no evidence of tumour recurrence.

CONCLUSIONS

This is the first report of a CLM arising in a small pox scar. Although the extended time interval between scarring and malignant changes makes it difficult to advise strict follow-up for patients with small pox scars, one should be aware that atypical changes and/or symptoms occurring in a small pox scar could potentially mean malignant transformation.

p53 Alterations and Their Relationship to SDHD Mutations in Parasympathetic Paragangliomas

Experimental and observational evidence suggests that chronic hypoxic stimulation can induce parasympathetic paraganglioma. This is emphasized by the identification of germline mutations in genes of the mitochondrial succinate dehydrogenase enzyme complex II in hereditary paraganglioma. Because of inactivating mutations in the succinate dehydrogenase subunit B (SDHB), C (SDHC), or D (SDHD) gene, the paraganglia undergo a chronic hypoxic stimulus leading to proliferation of the paraganglionic cells. Hypoxia is a known inducer of p53 up-regulation, which triggers cell cycle arrest and apoptosis. Inactivation of the p53 pathway, by gene mutation or by MDM2 overexpression, would enable cells to escape from cell cycle arrest and apoptosis and could contribute to tumorigenesis. To determine whether p53 inactivation plays a role in paraganglioma tumorigenesis, we investigated a series of 43 paragangliomas from 41 patients (of whom 24 patients harbored a germline SDHD mutation) for mutations in p53 exons 5-8 by PCR-SSCP. In addition, these tumors were investigated for p53 and MDM2 protein expression by immunohistochemistry, and the results were compared with clinical data and the presence of SDHD mutations. No aberrations in p53 exons 5-8 were found. The immunohistochemical experiments showed nuclear p53 expression in 15 tumors. Three tumors were positive for MDM2 that were also positive for p53. There was no correlation between p53 and MDM2 expression and clinical data or SDHD status. Given the fact that hypoxia induces p53 expression and regarding the absence of p53 mutations, these results suggest that p53 inactivation does not play a major role in the tumorigenesis of hereditary and sporadic paragangliomas.