SCP2 variant is associated with alterations in lipid metabolism, brainstem neurodegeneration, and testicular defects.

BACKGROUND: The detoxification of very long-chain and branched-chain fatty acids and the metabolism of cholesterol to form bile acids occur largely through a process called peroxisomal ß-oxidation. Mutations in several peroxisomal proteins involved in ß-oxidation have been reported, resulting in diseases characterized by neurological defects. The final step of the peroxisomal ß-oxidation pathway is catalyzed by sterol carrier protein-x (SCPx), which is encoded by the SCP2 gene. Previously, there have been two reports of SCPx deficiency, which resulted from a homozygous or compound heterozygous SCP2 mutation. We report herein the first patient with a heterozygous SCP2 mutation leading to SCPx deficiency. RESULTS: Clinical presentations of the patient included progressive brainstem neurodegeneration, cardiac dysrhythmia, muscle wasting, and azoospermia. Plasma fatty acid analysis revealed abnormal values of medium-, long-, and very long-chain fatty acids. Protein expression of SCPx and other enzymes involved in ß-oxidation were altered between patient and normal fibroblasts. RNA sequencing and lipidomic analyses identified metabolic pathways that were altered between patient and normal fibroblasts including PPAR signaling, serotonergic signaling, steroid biosynthesis, and fatty acid degradation. Treatment with fenofibrate or 4-hydroxytamoxifen increased SCPx levels, and certain fatty acid levels in patient fibroblasts. CONCLUSIONS: These findings suggest that the patient's SCP2 mutation resulted in decreased protein levels of SCPx, which may be associated with many metabolic pathways. Increasing SCPx levels through pharmacological interventions may reverse some effects of SCPx deficiency. Collectively, this work provides insight into many of the clinical consequences of SCPx deficiency and provides evidence for potential treatment strategies.

Endoscopic endonasal surgery for prolactinomas: prognostic factors for disease control and management of persistent disease.

Only a limited number of studies have focused on the results of the Endoscopic Endonasal Approach (EEA) for treatment of prolactinomas. We sought to assess the effectiveness of EEA for prolactinoma surgery, identify factors for disease remission, and present our approach for the management of persistent disease. Forty-seven prolactinomas operated over 10 years, with a mean follow-up of 59.9 months, were included. The primary endpoints were early disease remission and remission at last follow-up. Resistance/intolerance to DA were surgical indications in 76.7%. Disease remission was achieved in 80% of microprolactinomas and 100% of microprolactinomas enclosed by the pituitary. Early disease remission was correlated with female gender (p=0.03), lower preoperative PRL levels (p=0.014), microadenoma (p=0.001), lack of radiological hemorrhage (p=0.001), absence of cavernous sinus (CS) invasion (p<0.001), and extent of resection (EOR) (p<0.001). Persistent disease was reported in 48.9% of patients, with 47% of them achieving remission at last follow-up with DA therapy alone. Repeat EEA and/or radiotherapy were utilized in 6 patients, with 66.7% achieving remission. Last follow-up remission was achieved in 76.6%, with symptomatic improvement in 95.8%. Factors predicting last follow-up remission were no previous operation (p=0.001), absence of CS invasion (p=0.01), and EOR (p<0.001). Surgery is effective for disease control in microprolactinomas. In giant and invasive tumors, it may significantly reduce the tumor volume. A multidisciplinary approach may lead to long-term disease control in three-quarters of patients, with symptomatic improvement in an even greater proportion.

Pituitary neuroendocrine tumors: a model for neuroendocrine tumor classification.

The classification of adenohypophysial neoplasms as "pituitary neuroendocrine tumors" (PitNETs) was proposed in 2017 to reflect their characteristics as epithelial neuroendocrine neoplasms with a spectrum of clinical behaviors ranging from small indolent lesions to large, locally invasive, unresectable tumors. Tumor growth and hormone hypersecretion cause significant morbidity and mortality in a subset of patients. The proposal was endorsed by a WHO working group that sought to provide a unified approach to neuroendocrine neoplasia in all body sites. We review the features that are characteristic of neuroendocrine cells, the epidemiology and prognosis of these tumors, as well as further refinements in terms used for other pituitary tumors to ensure consistency with the WHO framework. The intense study of PitNETs has provided information about the importance of cellular differentiation in tumor prognosis as a model for neuroendocrine tumors in different locations.

Prolactin, a potential biomarker for chronic GVHD activity.

INTRODUCTION: The polypeptide prolactin (PRL) is a peptide hormone and a cytokine mostly secreted from the anterior pituitary gland. PRL is also synthesized in extra pituitary tissues including thymocytes and T lymphocytes. Considering the need for chronic GVHD (cGVHD) biomarkers, we explored the relationship between hyperprolactinemia and active cGVHD in a cohort of long-term post-alloHCT survivors. METHODS: Three-hundred sixteen adults underwent alloHCT between 2010 and 2016, survived more than 1 year and were included. All patients underwent a regular annual assessment that includes a hormone profile with serum PRL levels. RESULTS: Overall, 236 (74.7%) patients had cGVHD, and in 199 (63%), the grade was moderate or severe. Sixty-five (21%) recipients had active cGVHD at the time of the annual evaluation, and hyperprolactinemia was documented in 63 (19.9%) patients. Hyperprolactinemia correlated with cGVHD activity (Odds Ratio 6.9 (95% CI; 3.6-13.1); P < .001) in the multivariate analysis. In conclusion, patients with hyperprolactinemia were 6.4 times more likely to have active cGVHD in comparison with those patients with normal levels of PRL (P < .001). CONCLUSION: Prolactin may serve as a biomarker for cGVHD activity. Further studies are required to confirm these findings, and to explore if hyperprolactinemia has an impact on cGVHD severity and prognosis.

A phase 2 trial of sunitinib in patients with progressive paraganglioma or pheochromocytoma: the SNIPP trial.

BACKGROUND: Pheochromocytoma (PCC) and paraganglioma (PGL) are uncommon neoplasms with high morbidity in advanced stages. Effective systemic treatments are limited. METHODS: A multisite phase 2 trial evaluated sunitinib in patients with progressive PCC/PGL. Patients received 50 mg orally for 4-6 weeks. RESULTS: Between May 2009 and May 2016, 25 patients were enroled. The median age was 50 years and 56% were male. Three patients (12%) received prior chemotherapy and 16 (64%) prior surgery. The DCR was 83% (95% CI: 61-95%) and median PFS 13.4 (95% CI: 5.3-24.6) months. Of 23 evaluable patients, 3 (13%) with germline mutations (SDHA, SDHB, RET) achieved a PR. The patient with mutated RET and MEN2A remains on treatment after 64 cycles. The median time on treatment was 12.4 (1-88.0) months. Grade 3 or 4 toxicities were as expected and manageable; fatigue (16%) and thrombocytopenia (16%) were most common. One patient with grade 3 hypertension and 2 with grade 3 cardiac events discontinued treatment. CONCLUSION: Although the primary endpoint of disease control was met, the overall response rate of sunitinib was low in unselected patients with progressive PCC/PGL. Patients with germline variants in RET or in the subunits of SDH may derive greatest benefit.

Papillary Thyroid Cancers with Focal Tall Cell Change are as Aggressive as Tall Cell Variants and Should Not be Considered as Low-Risk Disease.

BACKGROUND: The tall cell variant of papillary thyroid carcinoma (PTC) is as an aggressive histological variant. The proportion of tall cells needed to influence prognosis is debated. METHODS: Patients with PTC and tall cells, defined as having a height-to-width ratio of ≥ 3:1, seen at a high-volume center between 2001 and 2015, were reviewed. Specimens were classified as (1) focal tall cell change, containing < 30% of tall cells; (2) tall cell variant, ≥ 30% of tall cells; and (3) control cases selected from infiltrative classical PTCs without adverse cytologic features. Univariate, sensitivity, and multivariate analyses were performed with persistent/recurrent disease as the primary outcome. RESULTS: We identified 96 PTCs with focal tall cell change, 35 with the tall cell variant and 104 control cases. Factors associated with poor clinical prognosis were significantly greater in those with focal tall cell change and tall cell variants. Regarding primary outcome, hazard ratios were 2.3 (95% confidence interval [CI] 1.0-5.7) for focal tall cell change, and 3.4 (95% CI 1.2-8.7) for tall cell variants compared with controls. Five-year disease-free survival was higher for the control group (92.7%, CI 87.4-98.0) compared with focal tall cell change (76.3%, CI 66.1-86.5) and the tall cell variant (62.2%, CI 43.2-81.2). When stratified in groups consisting of tall cell proportions (< 10%, 10-19%, 20-29% and ≥ 30%), identification of ≥ 10% tall cell change was associated with worse outcome (p = 0.002). CONCLUSIONS: PTCs with ≥ 10% tall cell change have worse prognosis than those without tall cells. Our data indicate that thyroid cancer management guidelines should consider PTCs with focal tall cell change outside of the low-risk classification.

Comprehensive characterization of a Canadian cohort of von Hippel-Lindau disease patients.

Von Hippel-Lindau disease (VHL) is a heritable condition caused by pathogenic variants in VHL and is characterized by benign and malignant lesions in the central nervous system (CNS) and abdominal viscera. Due to its variable expressivity, existing efforts to collate VHL patient data do not adequately capture all VHL manifestations. We developed a comprehensive and standardized VHL database in the web-based application, REDCap, that thoroughly captures all VHL manifestation data. As an initial trial, information from 86 VHL patients from the University Health Network/Hospital for Sick Children was populated into the database. Analysis of this cohort showed missense variants occurring with the greatest frequency, with all variants localizing to the α- or ß-domains of VHL. The most prevalent manifestations were central nervous system (CNS), renal, and retinal neoplasms, which were associated with frameshift variants and large deletions. We observed greater age-related penetrance for CNS hemangioblastomas with truncating variants compared to missense, while the reverse was true for pheochromocytomas. We demonstrate the utility of a comprehensive VHL database, which supports the standardized collection of clinical and genetic data specific to this patient population. Importantly, we expect that its web-based design will facilitate broader international collaboration and lead to a better understanding of VHL.

ENDOCRINE COMPLICATIONS IN PATIENTS WITH GVHD.

Objective: Graft-versus-host disease (GVHD) is an immune phenomenon that occurs in 30 to 70% of patients after allogeneic hematopoietic stem cell transplantation (HST). Chronic GVHD is a state of immune dysregulation wherein, depending on the severity and organ involved, patients may require prolonged treatment with additional or higher corticosteroids and other immunosuppressive agents. The objective of this study was to review the endocrine manifestations following HST that can arise as a consequence of the primary disease or its treatment, including chemotherapeutic agents, corticosteroids, radiation, or GVHD. Methods: We performed a narrative review of GVHD after HST. An English-language search for relevant studies was conducted on PubMed from inception to August 1, 2018, using the following search terms: "endocrine complications," "bone marrow transplantation," "graft-versus-host disease," and "GVHD." The reference lists of relevant studies were also reviewed. Results: Chronic GVHD may be associated with considerable pediatric growth impairment and may also contribute to thyroid gland dysfunction and thyroid cancer. These patients may also be at increased risk for low bone mineral density, reduced fertility, metabolic syndrome, and suppression of the pituitary-adrenal axis with adrenal insufficiency. Conclusion: This review indicates the importance of monitoring, diagnosing, and properly treating the endocrine complications in this population. More studies are needed to investigate the independent impact of GVHD on the endocrine system and treatment for complications. Abbreviations: BMD = bone mineral density; GH = growth hormone; GVHD = graft-versus-host disease; HST = hematopoietic stem cell transplantation; IGF-1 = insulin-like growth factor 1.

PREDICTIVE MARKERS FOR POSTSURGICAL MEDICAL MANAGEMENT OF ACROMEGALY: A SYSTEMATIC REVIEW AND CONSENSUS TREATMENT GUIDELINE.

Objective: To clarify the selection of medical therapy following transsphenoidal surgery in patients with acromegaly, based on growth hormone (GH)/insulin-like growth factor 1 (IGF-1) response and glucometabolic control. Methods: We carried out a systematic literature review on three of the best studied and most practical predictive markers of the response to somatostatin analogues (SSAs): somatostatin receptor (SSTR) expression, tumor morphologic classification, and T2-weighted magnetic resonance imaging (MRI) signal intensity. Additional analyses focused on glucose metabolism in treated patients. Results: The literature survey confirmed significant associations of all three factors with SSA responsiveness. SSTR expression appears necessary for the SSA response; however, it is not sufficient, as approximately half of SSTR2-positive tumors failed to respond clinically to first-generation SSAs. MRI findings (T2-hypo-intensity) and a densely granulated phenotype also correlate with SSA efficacy, and are advantageous as predictive markers relative to SSTR expression alone. Glucometabolic control declines with SSA monotherapy, whereas GH receptor antagonist (GHRA) monotherapy may restore normoglycemia. Conclusion: We propose a decision tree to guide selection among SSAs, dopamine agonists (DAs), and GHRA for medical treatment of acromegaly in the postsurgical setting. This decision tree employs three validated predictive markers and other clinical considerations, to determine whether SSAs are appropriate first-line medical therapy in the postsurgical setting. DA treatment is favored in patients with modest IGF-1 elevation. GHRA treatment should be considered for patients with T2-hyperintense tumors with a sparsely granulated phenotype and/or low SSTR2 staining, and may also be favored for individuals with diabetes. Prospective analyses are required to test the utility of this therapeutic paradigm. Abbreviations: DA = dopamine agonist; DG = densely granulated; GH = growth hormone; GHRA = growth hormone receptor antagonist; HbA1c = glycated hemoglobin; IGF-1 = insulin-like growth factor-1; MRI = magnetic resonance imaging; SG = sparsely granulated; SSA = somatostatin analogue; SSTR = somatostatin receptor.

Tools for Enhancement and Quality Improvement of Peer Assessment and Clinical Care in Endocrinology and Metabolism.

Members of the College of Physicians and Surgeons of Ontario Endocrinology and Metabolism Peer Review Network have been involved in a quality improvement project to help standardize the peer assessment of physicians practicing in endocrinology and metabolism. This has included developing state-of-the-art summaries of common endocrine problems by Canadian experts in endocrinology and metabolism. These tools have been developed in response to the educational needs, as identified by peer reviewers, of practicing endocrinologists in Ontario. These pedagogical tools aim not only to standardize the documentation of the clinical performance of endocrinologists but also to make the process more transparent and to improve the quality of patient care in Ontario. This article summarizes the project and also provides the tools developed for the endocrinology and metabolism section of the College of Physicians and Surgeons of Ontario.

Primary mediastinal paraganglioma associated with a familial variant in the succinate dehydrogenase B subunit gene.

Surgical management is the mainstay of therapy for primary cardiac tumors, yet due to the rarity of these malignancies, their management and workup remains a challenge. Here, we report a unique case of a patient with a primary left ventricular cardiac paraganglioma (PGL) and describe the role of a medical genetics assessment leading to the identification of a rare variant in the SDHB gene to be the causative etiology of this cardiac tumor. Due to decreasing costs and accessibility of molecular genetic analysis, genetic testing may become an emerging diagnostic adjunct in cases of cardiac tumors.

Silent subtype 3 pituitary adenomas are not always silent and represent poorly differentiated monomorphous plurihormonal Pit-1 lineage adenomas.

Originally classified as a variant of silent corticotroph adenoma, silent subtype 3 adenomas are a distinct histologic variant of pituitary adenoma of unknown cytogenesis. We reviewed the clinical, biochemical, radiological, immunohistochemical and ultrastructural features of 31 silent subtype 3 adenomas to clarify their cellular origin. Among 25 with clinical and/or radiological data, all were macroadenomas; there was cavernous sinus invasion in 30% of cases and involvement of the clivus in 17% of cases. Almost 90% of patients were symptomatic; 67% had mass effect symptoms, 37% were hypogonadal and 8% had secondary adrenal insufficiency. Significant hormonal excess in 29% of cases included hyperthyroidism in 17%, acromegaly in 8% and hyperprolactinemia above 150 µg/l in 4%. Two individuals with hyperprolactinemia who were younger than 30 years had multiple endocrine neoplasia type 1. Immunohistochemically, all 31 tumors were diffusely positive for the pituitary lineage-specific transcription factor Pit-1. Although three only expressed Pit-1, others revealed variable positivity for one or more hormones of Pit-1 cell lineage (growth hormone, prolactin, thyroid-stimulating hormone), as well as alpha-subunit and estrogen receptor. Most tumors exhibited perinuclear reactivity for keratins with the CAM5.2 antibody; scattered fibrous bodies were noted in five (16%) tumors. The mean MIB-1 labeling index was 4% (range, 1-9%). Fourteen cases examined by electron microscopy were composed of a monomorphous population of large polygonal or elongated cells with nuclear spheridia. Sixty-five percent of patients had residual disease after surgery; after a mean follow-up of 48.4 months (median 41.5; range=2-171) disease progression was documented in 53% of those cases. These data identify silent subtype 3 adenomas as aggressive monomorphous plurihormonal adenomas of Pit-1 lineage that may be associated with hyperthyroidism, acromegaly or galactorrhea and amenorrhea. Our findings argue against the use of the nomenclature 'silent' for these tumors. To better reflect the characteristics of these tumors, we propose that they be classified as 'poorly differentiated Pit-1 lineage adenomas'.

PANCREATIC INCIDENTALOMAS: IS IT NET OR NOT?

ABBREVIATIONS: FNA = fine-needle aspirate IPAS = intrapancreatic accessory spleen PNET = pancreatic neuroendocrine tumor.

A detailed spatial analysis on contrasting cancer incidence patterns in thyroid and lung cancer in Toronto women.

BACKGROUND: Thyroid cancer has been rapidly rising in incidence in Canada; however, in contrast, lung cancer appears to be decreasing in incidence in Canadian men and stable in women. Moreover, disease-related mortality risk is generally very low in TC but high in LC. We performed a geographic spatial analysis in metropolitan Toronto, Canada to determine if there is regional variability of respective risks of thyroid cancer (TC) and lung cancer (LC), among women. Women were of particular interest for this study, given their known predilection for thyroid cancer. METHODS: The postal codes of all females with TC or LC, residing in metropolitan Toronto from 2004 to 2008, were geocoded to point locations according to 2006 Canadian Census data. The data were analysed using a log-Gaussian Cox Process, where the intensity of age-adjusted cancer cases was modelled as a log-linear combination of the population at risk, explanatory variables (race, immigration, and median household income), and a residual spatially varying random effect. For each respective malignancy, statistical models were fit to make quantify the relationship between cancer incidence and explanatory variables. RESULTS: We included 2230 women with TC and 2412 with LC. The distribution of TC and LC cases contrasted inversely among Toronto neighbourhoods with the highest TC incidence in the Northeast and the highest LC incidence in the Southeast. A higher proportion of Asian ethnicity was associated with higher regional risk of TC and lower risk of LC. A higher proportion of recent immigrants was associated with increased LC and lower TC risk, whereas median household income and proportions of African ethnicity were not significantly associated with risk of either cancer, after adjustment for other socio-demographic variables. CONCLUSIONS: We observed contrasting regional distributions of female TC and LC cases in Toronto. The differences were partly attributed to ethnic composition variability and the proportion of recent immigrants, but substantial unexplained residual variation of incidence patterns of these malignancies exists, suggesting that more individual-level research is needed to explain the regional variability of incidence of these malignancies.

Thyroid cancer patient perceptions of radioactive iodine treatment choice: Follow-up from a decision-aid randomized trial.

BACKGROUND: Patient decision aids (P-DAs) inform medical decision making, but longer term effects are unknown. This article describes extended follow-up from a thyroid cancer treatment P-DA trial. METHODS: In this single-center, parallel-design randomized controlled trial conducted at a Canadian tertiary/quaternary care center, early-stage thyroid cancer patients from a P-DA trial were contacted 15 to 23 months after randomization/radioactive iodine (RAI) decision making to evaluate longer term outcomes. It was previously reported that the use of the computerized P-DA in thyroid cancer patients considering postsurgical RAI treatment significantly improved medical knowledge in comparison with usual care alone. The P-DA and control groups were compared for the following outcomes: feeling informed about the RAI treatment choice, decision satisfaction, decision regret, cancer-related worry, and physician trust. In a subgroup of 20 participants, in-depth interviews were conducted for a qualitative analysis. RESULTS: Ninety-five percent (70 of 74) of the original population enrolled in follow-up at a mean of 17.1 months after randomization. P-DA users perceived themselves to be significantly more 1) informed about the treatment choice (P = .008), 2) aware of options (P = .009), 3) knowledgeable about treatment benefits (P = .020), and 4) knowledgeable about treatment risks/side effects (P = .001) in comparison with controls. There were no significant group differences in decision satisfaction (P = .142), decision regret (P = .199), cancer-related worry (P = .645), mood (P = .211), or physician trust (P = .764). In the qualitative analysis, the P-DA was perceived to have increased patient knowledge and confidence in decision making. CONCLUSIONS: The P-DA improved cancer survivors' actual and long-term perceived medical knowledge with no adverse effects. More research on the long-term outcomes of P-DA use is needed.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS, AMERICAN COLLEGE OF ENDOCRINOLOGY DISEASE STATE CLINICAL REVIEW: CLINICAL RELEVANCE OF MACROPROLACTIN IN THE ABSENCE OR PRESENCE OF TRUE HYPERPROLACTINEMIA.

OBJECTIVE: To review the current literature regarding the prevalence of macroprolactin (macroPRL) in hyperprolactinemic patients and determine recommendations for testing. METHODS: An electronic United States National Library of Medicine PubMed search (through October, 2014) was conducted for search term "macroprolactin." Only English-language articles were considered. RESULTS: MacroPRL is an under-recognized cause of elevated prolactin (PRL) and is present in approximately 4% to 40% of hyperprolactinemic patients depending on the referral population. Clinical findings which could be due to hyperprolactinemia are the impetus for testing for PRL. Because of this there is significant overlap in the clinical presentation of patients with true hyperprolactinemia and those with macroPRL, differentiation cannot always be made on the basis of symptoms. A lack of recognition of the presence of macroPRL can lead to unnecessary laboratory investigations, imaging, and pharmacologic or surgical treatment. CONCLUSION: Until there is a commercially available PRL assay that is not subject to interference by macroPRL, clinicians should consider the possibility of macroPRL, especially if the clinical presentation, imaging findings, and/or response to therapy reveal inconsistencies.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia.

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

Exploring the relationship between patients' information preference style and knowledge acquisition process in a computerized patient decision aid randomized controlled trial.

BACKGROUND: We have shown in a randomized controlled trial that a computerized patient decision aid (P-DA) improves medical knowledge and reduces decisional conflict, in early stage papillary thyroid cancer patients considering adjuvant radioactive iodine treatment. Our objectives were to examine the relationship between participants' baseline information preference style and the following: 1) quantity of detailed information obtained within the P-DA, and 2) medical knowledge. METHODS: We randomized participants to exposure to a one-time viewing of a computerized P-DA (with usual care) or usual care alone. In pre-planned secondary analyses, we examined the relationship between information preference style (Miller Behavioural Style Scale, including respective monitoring [information seeking preference] and blunting [information avoidance preference] subscale scores) and the following: 1) the quantity of detailed information obtained from the P-DA (number of supplemental information clicks), and 2) medical knowledge. Spearman correlation values were calculated to quantify relationships, in the entire study population and respective study arms. RESULTS: In the 37 P-DA users, high monitoring information preference was moderately positively correlated with higher frequency of detailed information acquisition in the P-DA (r = 0.414, p = 0.011). The monitoring subscale score weakly correlated with increased medical knowledge in the entire study population (r = 0.268, p = 0.021, N = 74), but not in the respective study arms. There were no significant associations with the blunting subscale score. CONCLUSIONS: Individual variability in information preferences may affect the process of information acquisition from computerized P-DA's. More research is needed to understand how individual information preferences may impact medical knowledge acquisition and decision-making.

Tyrosine kinase receptors as molecular targets in pheochromocytomas and paragangliomas.

Pheochromocytomas and paragangliomas are neuroendocrine tumors shown to be responsive to multitargeted tyrosine kinase inhibitor (TKI) treatment. Despite growing knowledge regarding their genetic basis, the ability to predict behavior in these tumors remains challenging. There is also limited knowledge of their tyrosine kinase receptor expression and whether the clinical response observed to the TKI sunitinib relates only to its anti-angiogenic properties or also due to a direct effect on tumor cells. To answer these questions, an in vitro model of sunitinib treatment of a pheochromocytoma cell line was created. Sunitinib targets (VEGFRs, PDGFRs, and C-KIT), FGFRs, and cell cycle regulatory proteins were investigated in human tissue microarrays. SDHB immunohistochemistry was used as a surrogate marker for the presence of succinate dehydrogenase mutations. The FGFR4 G388R single nucleotide polymorphism was also investigated. Sunitinib treatment in vitro decreases cell proliferation mainly by targeting cell cycle, DNA metabolism, and cell organization genes. FGFR1, -2, and -4, VEGFR2, PDGFRα, and p16 were overexpressed in primary human pheochromocytomas and paragangliomas. Discordant results were observed for VEGFR1, p27, and p21 overexpressed in paragangliomas but underexpressed in pheochromocytomas; PDGFRß, Rb, and Cyclin D1 overexpressed in paragangliomas only; and FGFR3 overexpressed in pheochromocytomas and underexpressed in paragangliomas. Low expression of C-KIT, p53, and Aurora kinase A and B was observed. Nuclear FGFR2 expression was associated with increased risk of metastasis (odds ratio (OR)=7.61, P=0.008), as was membranous PDGFRα (OR=13.71, P=0.015), membranous VEGFR1 (OR=8.01, P=0.037), nuclear MIB1 (OR=1.26, P=0.008), and cytoplasmic p27 (OR=1.037, P=0.030). FGFR3, VEGFR2, and C-KIT levels were associated with decreased risk of metastasis. We provide new insights into the mechanistic actions of sunitinib in pheochromocytomas and paragangliomas, and support current evidence that multitargeted TKIs might be a suitable treatment alternative for these tumors.