Goswin Y. Meyer-Rochow

Immunohistochemistry for SDHB triages genetic testing of SDHB, SDHC, and SDHD in paraganglioma-pheochromocytoma syndromes.

Up to 30% of pheochromocytomas and paragangliomas are associated with germline RET, Von Hippel-Lindau (VHL), neurofibromatosis type I (NF1), and succinate dehydrogenase subunits (SDHB, SDHC, and SDHD) mutations. Genetic testing allows familial counseling and identifies subjects at high risk of malignancy (SDHB mutations) or significant multiorgan disease (RET, VHL, or NF1). However, conventional genetic testing for all loci is burdensome and costly. We performed immunohistochemistry for SDHB on 58 tumors with known SDH mutation status. We defined positive as granular cytoplasmic staining (a mitochondrial pattern), weak diffuse as a cytoplasmic blush lacking definite granularity, and negative as completely absent staining in the presence of an internal positive control. All 12 SDH mutated tumors (6 SDHB, 5 SDHD, and 1 SDHC) showed weak diffuse or negative staining. Nine of 10 tumors with known mutations of VHL, RET, or NF1 showed positive staining. One VHL associated tumor showed weak diffuse staining. Of 36 tumors without germline mutations, 34 showed positive staining. One paraganglioma with no known SDH mutation but clinical features suggesting familial disease was negative, and one showed weak diffuse staining. We also performed immunohistochemistry for SDHB on 143 consecutive unselected tumors of which 21 were weak diffuse or negative. As SDH mutations are virtually always germline, we conclude that approximately 15% of all pheochromocytomas or paragangliomas are associated with germline SDH mutation and that immunohistochemistry can be used to triage genetic testing. Completely absent staining is more commonly found with SDHB mutation, whereas weak diffuse staining often occurs with SDHD mutation.

Pheochromocytoma: Current Approaches and Future Directions

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Because of the excess secretion of hormones, these tumors often cause debilitating symptoms and a poor quality of life. While medical management plays a significant role in the treatment of pheochromocytoma patients, surgical excision remains the only cure. Improved medical management and surgical techniques and an increased understanding of hereditary disease have improved the outcome of pheochromocytoma patients with benign disease; however, the outcome of patients with malignant disease remains poor. In this review, we discuss the presentation, diagnosis, management, and future directions in the management of this disease.

MicroRNA profiling of benign and malignant pheochromocytomas identifies novel diagnostic and therapeutic targets

MicroRNAs (miRNAs) are small RNAs ( approximately 22 bp) that post-transcriptionally regulate protein expression and are found to be differentially expressed in a number of human cancers. There is increasing evidence to suggest that miRNAs could be useful in cancer diagnosis, prognosis, and therapy. We performed miRNA microarray expression profiling on a cohort of 12 benign and 12 malignant pheochromocytomas and identified a number of differentially expressed miRNAs. These results were validated in a separate cohort of ten benign and ten malignant samples using real-time quantitative RT-PCR; benign samples had a minimum follow-up of at least 2 years. It was found that IGF2 as well as its intronic miR-483-5p was over-expressed, while miR-15a and miR-16 were under-expressed in malignant tumours compared with benign tumours. These miRNAs were found to be diagnostic and prognostic markers for malignant pheochromocytoma. The functional role of miR-15a and miR-16 was investigated in vitro in the rat PC12 pheochromocytoma cell line, and these miRNAs were found to regulate cell proliferation via their effect on cyclin D1 and apoptosis. These data indicate that miRNAs play a pivotal role in the biology of malignant pheochromocytoma, and represent an important class of diagnostic and prognostic biomarkers and therapeutic targets warranting further investigation.

The Utility of Metaiodobenzylguanidine Single Photon Emission Computed Tomography/Computed Tomography (MIBG SPECT/CT) for the Diagnosis of Pheochromocytoma

BackgroundThe enhancement of metaiodobenzylguanidine single photon emission computed tomography (MIBG SPECT) imaging through the addition of CT images fused with SPECT data (coregistered MIBG SPECT/CT imaging) is new technology that allows direct correlation of anatomical and functional information. We hypothesized that MIBG SPECT/CT imaging would provide additional information and improve diagnostic confidence for the radiological localization of a pheochromocytoma, in particular for patients at high risk of multifocal or recurrent disease.MethodsA retrospective study of all patients investigated by MIBG SPECT/CT at our institution from 2006 to 2008 for a suspected pheochromocytoma was performed. Each case was compared with conventional radiological investigations to determine whether MIBG SPECT/CT was able to improve diagnostic confidence and provide additional diagnostic information compared with conventional imaging alone.ResultsTwenty-two patients had MIBG SPECT/CT imaging for a suspected pheochromocytoma. Fourteen patients had positive MIBG SPECT/CT imaging results correlating with imaging by CT or magnetic resonance imaging in all cases. In six cases, MIBG SPECT/CT provided additional information that altered the original radiological diagnosis. Five patients with a pheochromocytoma-associated germline mutation had multifocal disease excluded by MIBG SPECT/CT. Patients without a germline mutation that had positive biochemistry and a solitary lesion with conventional imaging had no diagnostic improvement with MIBG SPECT/CT imaging.ConclusionsMIBG SPECT/CT fusion imaging is a sensitive and specific radiological imaging tool for patients suspected to have pheochromocytoma. The particular strengths of MIBG SPECT/CT are detection of local recurrence, small extra-adrenal pheochromocytomas, multifocal tumors, or the presence of metastatic disease.

Outcomes of Surgically Managed Pediatric Thyroid Cancer

BACKGROUND Thyroid cancer is the most common carcinoma in children, and compared with adults, generally present with more advanced disease. Management is similar between populations, primarily consisting of total thyroidectomy. With similar treatment despite disease severity, we chose to explore the surgical outcome of pediatric patients with thyroid malignancy. METHODS A review of medical records at two academic institutions revealed 68 patients<19 y of age who underwent surgical resection of a malignant thyroid nodule between 1962 and 2008. RESULTS Of 68 pediatric surgery patients identified with thyroid malignancy, 50 patients (74%) had a total thyroidectomy. Minor complications were noted in 21% of surgeries with 19% temporary hypocalcemia. Risk of complication was not associated with type of surgery. Patients receiving a lobectomy or subtotal thyroidectomy were at greater risk for needing a second surgical procedure, required by 14 patients (21%). CONCLUSIONS There was no significant increase in surgical complications with respect to type of surgery, however, patients receiving less than total thyroidectomy were at increased risk of repeat surgery. Total thyroidectomy is recommended as the standard of care for the management of pediatric thyroid cancer.

Increased SSTR2A and SSTR3 expression in succinate dehydrogenase-deficient pheochromocytomas and paragangliomas.

Many neuroendocrine tumors, including pheochromocytomas (PCs) and paragangliomas (PGLs), express one or more somatostatin receptors (SSTR1-5). A number of studies have reported SSTR expression in PCs and PGLs. However, receptor expression patterns have been conflicting, and until recently, specific monoclonal antibodies were not available against SSTR1-5. The aim of this study was to compare SSTR1-5 expression in succinate dehydrogenase (SDH)-deficient PCs and PGLs (defined as having absent SDHB immunostaining) to those tumors with normal SDHB staining. Immunohistochemistry for SDHB and SSTR1-5 was performed using specific monoclonal antibodies on archived formalin-fixed, paraffin-embedded tissue from patients who had undergone surgery for PC or PGLs. A total of 182 PC/PGLs were included (129 adrenal, 44 extra-adrenal, 9 metastases); 32 tumors were SDH deficient, whereas 150 tumors had positive SDHB staining. SDH-deficient tumors were more likely to demonstrate moderate or strong staining for SSTR2A and SSTR3 when compared with SDH-sufficient tumors (91% versus 49% [P < .0001] and 50% versus 21% [P = .0008], respectively). Immunostaining for the other SSTRs was not different between SDH-deficient and tumors with preserved SDHB staining. SSTR2A and SSTR3 are more likely to be expressed in SDH-deficient PC/PGLs as compared with tumors demonstrating normal SDHB staining pattern. These findings suggest that the role of somatostatin analogue therapy (unlabeled or radiolabeled) should be reexamined in the context of the underlying SDHB immunohistochemistry pattern.

Denaturing high performance liquid chromatography detection of SDHB, SDHD, and VHL germline mutations in pheochromocytoma.

BACKGROUND Pheochromocytomas are neuroendocrine tumors of chromaffin cell origin which arise from the adrenal medulla and less commonly the extra-adrenal sympathetic paraganglia. Pheochromocytomas are component tumors of the familial syndromes multiple endocrine neoplasia Type 2, von Hippel Lindau disease, Neurofibromatosis Type 1, and the pheochromocytoma/paraganglioma syndromes caused by mutations in the RET, VHL, NF1, SDHB, and SDHD genes, respectively. The aim of this study was to evaluate denaturing high performance liquid chromatography (dHPLC) as a screening tool for the detection of germline mutations within VHL, SDHB, and SDHD in pheochromocytoma patients. METHODS Polymerase chain reaction of all exons of VHL, SDHB, and SDHD genes was performed on leukocyte DNA extracted from stored blood samples of 74 unrelated patients treated for pheochromocytoma. After dHPLC analysis, all samples demonstrating variance were selected for sequencing. RESULTS Of the 74 patients, 12 mutations and 16 polymorphisms were identified by dHPLC and confirmed on sequencing. More specifically, a total of 5 mutations and 15 polymorphisms were detected in SDHB and 7 mutations and 1 polymorphism were identified in VHL. No SDHD mutations or polymorphisms were identified. By sequencing only dHPLC variants, the total amount of DNA sequencing required was reduced by approximately 88%. CONCLUSIONS dHPLC is an effective screening tool for the detection of germline mutations in SDHB, SDHD, and VHL and has application for diagnostic germline mutation analysis in pheochromocytoma patients.

Outcomes of minimally invasive surgery for phaeochromocytoma

Laparoscopic adrenalectomy is now accepted as the procedure of choice for the resection of benign adrenocortical tumours, but few studies have assessed whether the outcomes of laparoscopic adrenalectomy for adrenal phaeochromocytoma are similar to that of other adrenal tumour types. This is a retrospective cohort study. Clinical and operative data were obtained from an adrenal tumour database and hospital records. A total of 191 patients had laparoscopic adrenalectomy, of which 36 were for phaeochromocytoma, over a 12‐year period. Length of hospital stay (4.8 vs 3.6 days, P= 0.03) and total operating times (183 vs 157 min, P= 0.01) were greater in the laparoscopic phaeochromocytoma resection group. Despite the greater size of the phaeochromocytomas compared to the remaining adrenal tumour types (44 mm vs 30 mm, P < 0.01), however, rate of conversion and morbidity were no different. Laparoscopic adrenalectomy for phaeochromocytoma is a safe procedure with similar outcomes to laparoscopic adrenalectomy for other adrenal tumour types.

Overexpression of miR-210 is associated with SDH-related pheochromocytomas, paragangliomas, and gastrointestinal stromal tumours

miR-210 is a key regulator of response to hypoxia. Pheochromocytomas (PCs) and paragangliomas (PGLs) with germline SDHx or VHL mutations have pseudohypoxic gene expression signatures. We hypothesised that PC/PGLs containing SDHx or VHL mutations, and succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours (GISTs), would overexpress miR-210 relative to non-SDH or -VHL-mutated counterparts. miR-210 was analysed by quantitative PCR in i) 39 PC/PGLs, according to genotype (one SDHA, five SDHB, seven VHL, three NF1, seven RET, 15 sporadic, one unknown) and pathology (18 benign, eight atypical, 11 malignant, two unknown); ii) 18 GISTs, according to SDHB immunoreactivity (nine SDH-deficient and nine SDH-proficient) and iii) two novel SDHB-mutant neurosphere cell lines. miR-210 was higher in SDHx- or VHL-mutated PC/PGLs (7.6-fold) compared with tumours without SDHx or VHL mutations (P=0.0016). miR-210 was higher in malignant than in unequivocally benign PC/PGLs (P=0.05), but significance was lost when benign and atypical tumours were combined (P=0.08). In multivariate analysis, elevated miR-210 was significantly associated with SDHx or VHL mutation, but not with malignancy. In GISTs, miR-210 was higher in SDH-deficient (median 2.58) compared with SDH-proficient tumours (median 0.60; P=0.0078). miR-210 was higher in patient-derived neurosphere cell lines containing SDHB mutations (6.5-fold increase) compared with normal controls, in normoxic conditions (P<0.01). Furthermore, siRNA-knockdown of SDHB in HEK293 cells increased miR-210 by 2.7-fold (P=0.001) under normoxia. Overall, our results suggest that SDH deficiency in PC, PGL and GISTs induces miR-210 expression and substantiates the role of aberrant hypoxic-type cellular responses in the development of these tumours.

Thyroid cancer in Graves’ disease: is surgery the best treatment for Graves’ disease?

Graves’ disease is a common cause of thyrotoxicosis. Treatment options include anti‐thyroid medications or definitive therapy: thyroidectomy or radioactive iodine (I131). Traditionally, I131 has been the preferred definitive treatment for Graves’ disease in New Zealand. Reports of concomitant thyroid cancer occurring in up to 17% of Graves’ patients suggest surgery, if performed with low morbidity, may be the preferred option. The aim of this study was to determine the rate of thyroid cancer and surgical outcomes in a New Zealand cohort of patients undergoing thyroidectomy for Graves’ disease.