Diagnostic yield and clinical impact of germline sequencing in children with CNS and extracranial solid tumors-a nationwide, prospective Swedish study.

Background: Childhood cancer predisposition (ChiCaP) syndromes are increasingly recognized as contributing factors to childhood cancer development. Yet, due to variable availability of germline testing, many children with ChiCaP might go undetected today. We report results from the nationwide and prospective ChiCaP study that investigated diagnostic yield and clinical impact of integrating germline whole-genome sequencing (gWGS) with tumor sequencing and systematic phenotyping in children with solid tumors. Methods: gWGS was performed in 309 children at diagnosis of CNS (n = 123, 40%) or extracranial (n = 186, 60%) solid tumors and analyzed for disease-causing variants in 189 known cancer predisposing genes. Tumor sequencing data were available for 74% (227/309) of patients. In addition, a standardized clinical assessment for underlying predisposition was performed in 95% (293/309) of patients. Findings: The prevalence of ChiCaP diagnoses was 11% (35/309), of which 69% (24/35) were unknown at inclusion (diagnostic yield 8%, 24/298). A second-hit and/or relevant mutational signature was observed in 19/21 (90%) tumors with informative data. ChiCaP diagnoses were more prevalent among patients with retinoblastomas (50%, 6/12) and high-grade astrocytomas (37%, 6/16), and in those with non-cancer related features (23%, 20/88), and ≥2 positive ChiCaP criteria (28%, 22/79). ChiCaP diagnoses were autosomal dominant in 80% (28/35) of patients, yet confirmed de novo in 64% (18/28). The 35 ChiCaP findings resulted in tailored surveillance (86%, 30/35) and treatment recommendations (31%, 11/35). Interpretation: Overall, our results demonstrate that systematic phenotyping, combined with genomics-based diagnostics of ChiCaP in children with solid tumors is feasible in large-scale clinical practice and critically guides personalized care in a sizable proportion of patients. Funding: The study was supported by the Swedish Childhood Cancer Fund and the Ministry of Health and Social Affairs.

Health-related quality of life and physical activity in Nordic patients with moderate haemophilia A and B (the MoHem study).

INTRODUCTION: The impact of moderate haemophilia on health-related quality of life (HRQoL) and physical activity (PA) is not well known. In previous studies, persons with factor VIII/factor IX activity (FVIII/FIX:C) below 3 IU/dL were associated with a more severe bleeding phenotype than predicted. AIM: To explore HRQoL and PA in patients with moderate haemophilia A (MHA) and B (MHB). METHODS: A cross-sectional, multicentre study covering patients with MHA and MHB in Sweden, Finland, and Norway. HRQoL was assessed with the EuroQoL 5-Dimensions (EQ-5D) form and PA with the International Physical Activity Questionnaire among participants aged ≥15 years. RESULTS: We report on 104 patients aged 15-84 years from the MoHem study. Overall, EQ-5D utility was .85 (median) (Q1-Q3 0.73-1.0) with corresponding visual analogue scale (VAS) 80 (70-90), which were similar regardless of treatment modality, FVIII/FIX:C, and MHA or MHB. Pain and mobility were most frequently affected dimensions. Utility (r = -.54), VAS (r = -.42), and PA (r = -.32) correlated negatively with arthropathy (HJHS). Only patients aged 41-50 years displayed lower utility (p = .02) and VAS (p < .01) than the Norwegian population norm. Patients on prophylaxis aged 35-54 years reported higher PA than those treated on-demand (p = .01). CONCLUSION: Haemophilic arthropathy had negative impact on HRQoL and PA in Nordic patients with moderate haemophilia. Middle-aged patients captured lower utility and VAS than observed in the general population. Tailored prophylaxis and improved joint health may influence positively on HRQoL and PA also in moderate haemophilia.

Incidence of venous thromboembolic events not related to vascular catheters in a prospective cohort of critically ill children.

The risk for venous thromboembolism (VTE) is considered to be low in the general paediatric intensive care unit (PICU) population, and pharmacological thromboprophylaxis is not routinely used. PICU patients considered at high-risk of VTE could possibly benefit from pharmacological thromboprophylaxis, but the incidence of VTE in this group of patients is unclear. This was an observational, prospective study at a tertiary multi-disciplinary paediatric hospital. We used comprehensive ultrasonography screening for VTE in critically ill children with multiple risk factors for VTE. Patients admitted to PICU ≥ 72 h and with ≥ two risk factors for VTE were included. Patients receiving pharmacological thromboprophylaxis during their entire PICU stay were excluded. The primary outcome of the study was VTEs not related to the use of a CVC. Ultrasonography screening of the great veins was performed at PICU discharge. Seventy patients with median (interquartile range) 3 (2-4) risk factors for VTE were evaluated. Median age was 0.3 years (0.03-4.3) and median PICU length of stay 9 days (5-17). Regarding the primary outcome, no symptomatic VTEs occurred and no asymptomatic VTEs were found on ultrasonography screening, resulting in an incidence of VTEs not related to a vascular catheter of 0% (95% CI: 0-5.1%). CONCLUSION: Our results indicate that VTEs not related to a vascular catheter are a rare event even in a selected group of severely ill small children considered to be at high risk of VTE. WHAT IS KNOWN: • Children in the PICU often have several risk factors for venous thromboembolism (VTE). • The incidence of VTE in PICU patients is highly uncertain, and there are no evidence-based guidelines regarding VTE prophylaxis. WHAT IS NEW: • This study found an incidence of VTEs not related to a vascular catheter of 0% (95% CI: 0-5.1%). • This indicates that such VTE events are rare even in PICU patients with multiple risk factors for VTE.

Complications of Pediatric Midline Catheters: A Prospective Observational Pilot Study.

BACKGROUND: Midline catheters are peripheral intravenous (IV) catheters in which the tip of the catheter does not reach the central circulation. In children, the use of midline catheters could lead to decreased complications from central venous catheters. To validate the safety of midline catheter use in children, we aimed to describe the complications and dwell time of pediatric midline catheters. The primary outcome was the incidence of catheter-related venous thromboembolism (VTE). METHODS: We conducted an observational, prospective study including consecutive patients at a tertiary multidisciplinary pediatric hospital. One hundred pediatric midline catheters were followed for thrombotic, infectious, and mechanical complications. After catheter removal, Doppler ultrasonography was performed to detect asymptomatic VTE. RESULTS: The mean age was 6.0 years (standard deviation [SD], 4.7), and median catheter dwell time was 6 (4-8) days. Most midline catheters were inserted in arm veins, most commonly in the basilic vein (56%). Catheter-related VTE was diagnosed in 30 (30%; 95% confidence interval [CI], 21%-40%) cases, corresponding to an incidence rate of 39 (95% CI, 26-55) cases per 1000 catheter days. Eight of 14 saphenous vein catheters were complicated by VTE compared to 22 of 86 arm vein catheters, suggesting an imbalance in favor of arm vein insertion site. Two patients needed anticoagulation therapy due to catheter-related VTE. Thirty (30%) catheters were removed unintentionally or due to complications, 22 of these needed additional IV access to complete the intended therapy. No catheter-related bloodstream infection (95% CI, 0%-4%) occurred. Mechanical complications occurred in 33 (33%; 95% CI, 24%-43%) midline catheters. CONCLUSIONS: In children, thrombotic and mechanical complications of midline catheters are common, but only few VTEs are severe enough to warrant anticoagulation therapy. Systemic infectious complications are rare. Seventy-eight percent of patients did not need additional venous access to complete short-term IV therapy. Considering the rate of clinically relevant complications and the catheter dwell time, pediatric midline catheters could be an alternative to central venous access for short-term (5-10 days) IV therapy.

[Transfusions in pediatric care - common situations]. / Blodtransfusion inom pediatriken ­ de vanligaste situationerna.

Transfusions should be given for medical indications and based on the clinical context for the individual patient. Clinicians should follow the most current existing clinical guidelines. The neonatal hemostatic system differs significantly from that of children and adults. Still, healthy neonates have a balanced hemostatic system. Since the level of hemoglobin is critical to tissue oxygenation, it is important in the rapidly developing neonate. For preterm neonates, different red blood cell transfusion thresholds should be used based on postnatal age and illness severity. Most hemodynamically stable pediatric intensive care patients with a hemoglobin >70 g/L do not require transfusion. Pediatric massive transfusion protocols should exist in pediatric hospitals. At Karolinska University Hospital, red blood cells, fresh frozen plasma and platelets are transfused in a ratio of 20:20:10 mL/kg to children <50 kg. In liver disease, transfusions can lead to increased bleeding.

Haemophilia early arthropathy detection with ultrasound and haemophilia joint health score in the moderate haemophilia (MoHem) study.

INTRODUCTION: Detection of early arthropathy is crucial for the management of haemophilia, but data on moderate haemophilia are limited. Therefore, we evaluated joint health and treatment modalities in Nordic patients with moderate haemophilia A (MHA) and B (MHB). AIM: To explore and compare the Haemophilia Early Arthropathy Detection with Ultrasound (HEAD-US) and Haemophilia Joint Health Score (HJHS) to detect early arthropathy in moderate haemophilia. METHODS: A cross-sectional, multicentre study covering Nordic patients with MHA and MHB. Arthropathy was evaluated by HEAD-US and HJHS 2.1. RESULTS: We assessed 693 joints in 118 patients. HEAD-US scores (medians [interquartile ranges]) were as follows: elbows 0 points (0-0), knees 0 (0-0) and ankles 0 (0-1). Respectively, by HJHS: elbows 0 (0-1), knees 0 (0-1) and ankles 0 (0-1). Cartilage (14%) and bone (13%) were most commonly affected by HEAD-US. Frequent HJHS findings were crepitus on motion in knees (39%), and loss of flexion (23%) and extension (13%) in ankles. HEAD-US correlated strongly with HJHS (elbows r = .70, knees r = .60 and ankles r = .65), but 24% had discordant scores. Joints with HJHS zero points, 5% captured HEAD-US ≥1 point. Moreover, 26% had HJHS findings without HEAD-US pathology. Notably, 31% of knees had crepitus on motion and normal HEAD-US. CONCLUSION: Overall, the joints attained low scores implying good joint health. HEAD-US correlated strongly with HJHS. In 5%, HEAD-US detected subclinical pathology. Crepitus on motion was frequently reported despite normal HEAD-US, thus not necessarily reflecting arthropathy. HEAD-US therefore improves the joint assessment in moderate haemophilia.

Characteristics and outcome of pediatric renal cell carcinoma patients registered in the International Society of Pediatric Oncology (SIOP) 93-01, 2001 and UK-IMPORT database: A report of the SIOP-Renal Tumor Study Group.

In children, renal cell carcinoma (RCC) is rare. This study is the first report of pediatric patients with RCC registered by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Pediatric patients with histologically confirmed RCC, registered in SIOP 93-01, 2001 and UK-IMPORT databases, were included. Event-free survival (EFS) and overall survival (OS) were analyzed using the Kaplan-Meier method. Between 1993 and 2019, 122 pediatric patients with RCC were registered. Available detailed data (n = 111) revealed 56 localized, 30 regionally advanced, 25 metastatic and no bilateral cases. Histological classification according to World Health Organization 2004, including immunohistochemical and molecular testing for transcription factor E3 (TFE3) and/or EB (TFEB) translocation, was available for 65/122 patients. In this group, the most common histological subtypes were translocation type RCC (MiT-RCC) (36/64, 56.3%), papillary type (19/64, 29.7%) and clear cell type (4/64, 6.3%). One histological subtype was not reported. In the remaining 57 patients, translocation testing could not be performed, or TFE-cytogenetics and/or immunohistochemistry results were missing. In this group, the most common RCC histological subtypes were papillary type (21/47, 44.7%) and clear cell type (11/47, 23.4%). Ten histological subtypes were not reported. Estimated 5-year (5y) EFS and 5y OS of the total group was 70.5% (95% CI = 61.7%-80.6%) and 84.5% (95% CI = 77.5%-92.2%), respectively. Estimated 5y OS for localized, regionally advanced, and metastatic disease was 96.8%, 92.3%, and 45.6%, respectively. In conclusion, the registered pediatric patients with RCC showed a reasonable outcome. Survival was substantially lower for patients with metastatic disease. This descriptive study stresses the importance of full, prospective registration including TFE-testing.

Asymptomatic Right Atrial Thrombosis After Acute Lymphoblastic Leukemia Treatment.

Right atrial thrombosis is a rare, but potentially serious complication of acute lymphoblastic leukemia treatment. We conducted a retrospective multicenter study to assess the incidence, treatment, and outcome of asymptomatic right atrial thrombosis detected at routine echocardiography of children after acute lymphoblastic leukemia treatment in the Nordic and Baltic countries. Eleven (2.7%, 95% confidence interval, 1.4-4.9) of 406 patients had asymptomatic right atrial thrombosis, ranging from 10 to 25 mm at detection. Three patients were treated with anticoagulation. None of the thromboses affected cardiac function, and they showed neither sign of progress nor spontaneous or treatment-related regress at follow-up.

Safety and efficacy of nonacog alfa for the treatment of haemophilia B in children younger than 6 years of age in a routine clinical care setting: the EUREKIX registry study.

INTRODUCTION: European regulatory authorities request postmarketing safety and efficacy data for factor IX (FIX) products. AIM: Collect additional clinical data from routine nonacog alfa use in children aged <6 years with haemophilia B. METHODS: The EUREKIX registry included retrospective and prospective data collection phases. Safety was assessed via adverse drug reactions (ADRs)/adverse events (AEs) and events of special interest (ESIs) as the primary objective; efficacy was evaluated via annualised bleeding rates (ABRs). RESULTS: The retrospective phase comprised 37 subjects. Of these, 25 had severe haemophilia B. One subject experienced 2 ADRs; another experienced 4 ESIs of hypersensitivity. Median ABR in subjects receiving a predominantly on-demand regimen (prophylaxis <50% of time; n = 11) was 2.0; median ABR was 3.8 in those receiving predominantly prophylactic treatment (prophylaxis ≥50% of time; n = 24). Joint bleeding was infrequent (median ABR, 0.4; n = 35). The prospective phase included 26 subjects, with 17 continuing from the retrospective phase. A total of 20 subjects had severe haemophilia B. Three subjects experienced 7 treatment-related AEs; 3 experienced 4 ESIs. Median ABR was 4.5 and 1.1 in subjects who received predominantly on-demand (n = 5) or prophylactic treatment (n = 19), respectively; the overall median ABR for joint bleeding events was 0.0. CONCLUSIONS: Overall, nonacog alfa treatment effectively controlled bleeding events, with no new safety signals identified. These data support the safety and efficacy of nonacog alfa in routine clinical settings in children aged <6 years.

Joint health and treatment modalities in Nordic patients with moderate haemophilia A and B - The MoHem study.

INTRODUCTION: The prevalence of arthropathy in moderate haemophilia A (MHA) and B (MHB) is not well known. AIM: We evaluated joint health in Nordic patients in relation to their treatment modality. METHODS: A cross-sectional, multicentre study covering MHA and MHB in Sweden, Finland and Norway. Arthropathy was evaluated by ultrasound (HEAD-US) and Haemophilia Joint Health Score (HJHS). RESULTS: We report on 145 patients: median age 28 years (IQR 13-52) and 61% MHA. Baseline factor VIII/factor IX activity (FVIII/FIX:C) was 2 IU/dL (median) (IQR 2-4): lower for MHB (2 IU/dL, IQR 1-2) than MHA (3 IU/dL, IQR 2-4) (P < .01). Eighty-five per cent of MHA and 73% MHB had a history of haemarthrosis (P = .07). Age at first joint bleed was lower for MHA (5 years [median], IQR 3-7) than MHB (7 years, IQR 5-12) (P = .01). Thirty-eight per cent received prophylaxis, started at median 10 years of age (IQR 4-24). Median joint bleeds and serious other bleeds during the last 12 months were both zero (IQR 0-1). Total HEAD-US captured 0/48 points (median) (IQR 0-2) and HJHS 4/120 points (IQR 1-10) with strong correlation between them (r = .72). FVIII/FIX: C ≤ 3 IU/dL was associated with higher HJHS (P = .04). Fifteen per cent had undergone orthopaedic surgery. CONCLUSION: The current joint health in Nordic moderate haemophilia patients was rather good, but a subgroup had severe arthropathy. FVIII/FIX: C ≤ 3 IU/dL and MHA were associated with a more severe bleeding phenotype. We suggest primary prophylaxis to all patients with FVIII/FIX:C ≤ 3 IU/dL.

Incidence of and risk factors for venous thrombosis in children with percutaneous non-tunnelled central venous catheters.

BACKGROUND: Venous thrombosis (VT) in children is often associated with a central venous catheter (CVC). We aimed to determine the incidence of VT associated with percutaneous non-tunnelled CVCs in a general paediatric population, and to identify risk factors for VT in this cohort. METHODS: Observational, prospective study enrolling consecutive patients at a tertiary multi-disciplinary paediatric hospital. A total of 211 percutaneous, non-tunnelled CVCs were analysed. Data regarding potential risk factors for CVC-related VT were collected. Compression ultrasonography with colour Doppler was used to diagnose VT. RESULTS: Overall, 30.3% of children developed CVC-related VT, with an incidence rate of 29.6 (confidence interval, 22.5-36.9) cases/1000 CVC days. Upper body CVC location, multiple lumen CVCs, and male gender were independent risk factors for VT in multivariate analysis. All upper body VTs were in the internal jugular vein (IJV). The occurrence of CVC-related VT did not affect length of paediatric ICU or hospital stay. In patients with VT, femoral CVCs, young age, paediatric ICU admission, and a ratio of CVC/vein diameter >0.33 were associated with VT being symptomatic, occlusive, or both. IJV VT was often asymptomatic and non-occlusive. CONCLUSIONS: Paediatric non-tunnelled CVCs are frequently complicated by VT. Avoiding IJV CVCs and multiple lumen catheters could potentially reduce the overall risk of VT. However, IJV VT was more likely to be smaller and asymptomatic compared with femoral vein VT. More data are needed on the risk of complications from smaller, asymptomatic VT compared with the group of VT with symptoms or vein occlusion. Femoral vein CVCs and CVC/vein diameter >0.33 could be modifiable risk factors for VT with larger thrombotic mass. CLINICAL TRIAL REGISTRATION: ACTRN12615000442505.

Management of rivaroxaban- or apixaban-associated major bleeding with prothrombin complex concentrates: a cohort study.

There is uncertainty regarding the effectiveness and occurrence of thromboembolic events in patients treated with prothrombin complex concentrates (PCCs) for the management of major bleeding events (MBEs) on rivaroxaban or apixaban. We investigated the effectiveness of PCCs given for the management of MBEs in patients on rivaroxaban or apixaban. Between 1 January 2014 and 1 October 2016, we prospectively included patients on rivaroxaban or apixaban treated with PCCs for the management of MBEs. The effectiveness of PCCs was assessed by using the International Society of Thrombosis and Hemostasis Scientific and Standardization Subcommittee criteria for the assessment of the effectiveness of major bleeding management. The safety outcomes were thromboembolic events and all-cause mortality within 30 days after treatment with PCCs. A total of 84 patients received PCCs for the reversal of rivaroxaban or apixaban due to a MBE. PCCs were given at a median (interquartile range) dose of 2000 IU (1500-2000 IU). Intracranial hemorrhage (ICH) was the most common site of bleeding requiring reversal (n = 59; 70.2%), followed by gastrointestinal bleeding in 13 (15.5%) patients. Management with PCCs was assessed as effective in 58 (69.1%) patients and ineffective in 26 (30.9%) patients. Most patients with ineffective hemostasis with PCCs had ICH (n = 16; 61.5%). Two patients developed an ischemic stroke, occurring 5 and 10 days after treatment with PCC. Twenty-seven (32%) patients died within 30 days after a MBE. The administration of PCCs for the management of MBEs associated with rivaroxaban or apixaban is effective in most cases and is associated with a low risk of thromboembolism. Our findings are limited by the absence of a control group in the study.

Evaluation of a diagnostic algorithm for Heparin-Induced Thrombocytopenia.

INTRODUCTION: Heparin-Induced Thrombocytopenia (HIT) is a rare but serious immune-mediated complication of heparin treatment. HIT is characterized by an acute, transient prothrombotic state combined with thrombocytopenia and is caused by platelet-activating IgG antibodies that bind to complexes of heparin and platelet factor 4. The diagnosis of HIT relies on clinical presentation and the demonstration of HIT antibodies. One approach to improve the efficacy of laboratory analysis is to use a diagnostic algorithm. AIM: To evaluate one diagnostic algorithm for HIT where the 4 T's clinical risk score is combined with immunochemical and/or functional assays. MATERIALS AND METHODS: The quality of the diagnostic algorithm was retrospectively evaluated in 101 patients with suspected HIT. Laboratory results obtained from the diagnostic algorithm were compared to Heparin-Induced Platelet Aggregation (HIPA) and clinico-pathological evaluation of patients' medical records. RESULTS: We found that the algorithm had a diagnostic efficacy of 94%, with specificity of 94% and sensitivity 94%. Positive likelihood ratio (LR+) was 16.0, and the negative likelihood ratio (LR-) 15.5. The efficacy of PaGIA (n=95) was 0.46, and IgG-specific HPF4-abELISA (n=54) was 0.87. CONCLUSIONS: The diagnostic algorithm for HIT is sufficiently accurate and leads to in overall faster results and decreased cost of analysis. The weakest link of the algorithm is the risk of miscalculated 4T's scores, which is inevitably exacerbated by the insufficient experience most clinicians have with HIT. This highlights the importance of clear instructions from the laboratory and coagulation clinic.

Cerebral sinus venous thromboses in children with acute lymphoblastic leukaemia - a multicentre study from the Nordic Society of Paediatric Haematology and Oncology.

We present a prospective multicentre cohort of 20 children with acute lymphoblastic leukaemia (ALL) and cerebral sinus venous thrombosis (CSVT). The study covers a period of 5 years and comprises 1038 children treated according to the Nordic Society of Paediatric Haematology and Oncology (NOPHO) ALL 2008 protocol. The cumulative incidence of CSVT was 2%. Sixteen of the thromboses were related to asparaginase and 16 to steroids. Most CSVTs occurred in the consolidation phase. Nearly all were treated with low molecular weight heparin without bleeding complications. Mortality related to CSVT directly or indirectly was 10%, emphasizing the importance of this complication.

Antithrombin deficiency after prolonged asparaginase treatment in children with acute lymphoblastic leukemia.

Children with acute lymphoblastic leukemia (ALL) have several risk factors for deep venous thromboses (DVTs) such as central venous catheters and asparaginase (ASP), related antithrombin (AT) deficiency. After introduction of a new standard and intermediate-risk ALL treatment protocol with prolonged continuous ASP treatment, two symptomatic DVTs in 10 patients were observed at the Children's Hospital, Helsinki, Finland. To prevent further thrombotic complications yet ensuring continuous exposure to ASP, an AT substitution strategy was adopted in Helsinki. The same ALL treatment protocol is used without AT substitution in the other Nordic countries. In this retrospective study, we describe the effect of prolonged ASP treatment on AT and fibrinogen levels in children without AT substitution in Stockholm, Sweden (n = 39) and the AT substitution in children with AT activity below 0.55 kIU/l in Helsinki (n = 36, intervention group). The intervention group is compared with children treated similarly earlier in Helsinki without AT substitution (n = 10). The median lowest AT activity during the ASP treatment without AT substitution was 0.55 kIU/l. Fibrinogen level of 1.0 g/l or less was found in 14% of all routine samples during the ASP treatment. In the intervention group, 23 (64%) received AT concentrate. Two (20%) children had symptomatic DVT before initiation of the AT substitution and two (6%) thereafter. We conclude that most children are exposed to low AT activity during ASP treatment predisposing to thrombosis. The effect of prophylactic AT substitution remains unclear.

Deletions and altered expression of the RIZ1 tumour suppressor gene in 1p36 in pheochromocytomas and abdominal paragangliomas.

Pheochromocytomas and abdominal paragangliomas are rare catecholamine-producing tumours arising from neural crest-derived chromaffin cells. Frequent deletions of several distinct regions on the short arm of chromosome 1 suggest their involvement in the tumourigenesis process. The RIZ1 tumour suppressor encoded by the RIZ gene in 1p36.21 represents an attractive candidate target for the distal 1p deletions in these tumours. A panel of 18 pheochromocytomas (14 benign, and 4 malignant) and 11 abdominal paragangliomas (4 benign, and 7 malignant) were characterised for somatic deletions and mRNA expression status of RIZ1 using loss of heterozygosity (LOH) analysis and real-time quantitative PCR, respectively. Furthermore, we evaluated the methylation status of the RIZ1 promoter utilising methylation-specific PCR (MSP). Intragenic LOH at the RIZ locus was detected in 10 of 16 informative cases (62%), including 8 of 12 pheochromocytomas (67%) and 2 of 4 paragangliomas (50%). RIZ1 mRNA appeared to be significantly under-expressed in the tumour samples compared to normal adrenal controls (mean 0.6 vs. 1.0, p<0.001). This was not associated with RIZ1 promoter methylation in any of the samples, indicating that promoter hypermethylation is unlikely to be the underlying cause of the frequent expressional silencing. The recurrent inactivation of the tumour suppressor RIZ1 suggests that this event may be a significant contributing factor to tumour development in pheochromocytomas and abdominal paragangliomas.

Involvement of the PAX8/peroxisome proliferator-activated receptor gamma rearrangement in follicular thyroid tumors.

Recently, a translocation t(2; 3)(q13;p25), involving the fusion of PAX8 and peroxisome proliferator-activated receptor gamma (PPAR gamma) was suggested to arise only in follicular thyroid carcinomas. In this study, a group of 87 thyroid tumors were analyzed to determine the involvement of the PAX8/PPAR gamma fusion gene in these tumors, and also to determine whether this rearrangement can be used as a diagnostic marker for the differentiation between follicular thyroid carcinoma and adenoma. The PAX8/PPAR gamma rearrangement was detected by RT-PCR, fluorescence in situ hybridization, and/or Western analysis in 10 of 34 (29%) follicular thyroid carcinomas and in one of 20 (5%) atypical follicular thyroid adenomas, but not in any of the 20 follicular thyroid adenomas or 13 anaplastic thyroid carcinomas studied. In addition, seven of the 87 thyroid tumors exhibited involvement of PPAR gamma alone. Our findings suggest that PAX8/PPAR gamma occurs frequently in follicular thyroid carcinomas, and the presence of this rearrangement is likely to prove highly suggestive of a malignant tumor. Lack of the PAX8/PPAR gamma rearrangement in the anaplastic thyroid carcinoma group suggests that the tumorigenic pathway in these tumors is likely to be independent of this fusion. Furthermore, the results suggest that other rearrangements, involving PPAR gamma and other unidentified genes, may be involved in follicular thyroid tumorigenesis.