First-line avelumab for patients with PD-L1-positive metastatic or locally advanced urothelial cancer who are unfit for cisplatin.

BACKGROUND: Cisplatin-based chemotherapy is the most recommended treatment for metastatic urothelial cancer (mUC). However, about 50% of patients are considered to be cisplatin ineligible. Anti-programmed cell death protein 1/programmed death-ligand 1 (PD-L1) therapies have, nevertheless, increased the options available to clinicians and are especially valuable for treating these patients. This study therefore tested the activity and safety of avelumab as first-line therapy for mUC. PATIENTS AND METHODS: Patients with mUC who were ineligible for cisplatin-based chemotherapy were screened centrally for PD-L1 expression and only those with a tumour proportion score ≥ 5% were enrolled in the trial. The primary endpoint was 1-year overall survival (OS), and the secondary endpoints were median OS, median progression-free survival, overall response rate, duration of the response, safety and tolerability. All the survival rates were estimated with the Kaplan-Meier product-limit methodology and compared across groups using the log-rank test. RESULTS: A total of 198 patients were screened, with 71 (35.9%) whose PD-L1 expression was ≥5% enrolled in the study. The median age was 75 years, bladder cancer was the primary tumour in 73.2% of cases and 25.3% had liver metastases. The main reasons for the cisplatin ineligibility were a low rate of creatinine clearance (<60 ml/min), present in 70.4% of patients, and an Eastern Cooperative Oncology Group performance status of 2, which affected 31%. The median OS was 10.0 months (95% confidence interval 5.5-14.5 months) and 43% of patients were alive at 1 year. A complete response was achieved in 8.5% of cases, and 15.5% had a partial response. Adverse any-grade and high-grade events occurred in 49.3% and 8.5% of patients, respectively. A grade 3 infusion reaction was the only high-grade treatment-related adverse event. No treatment-related deaths were reported. CONCLUSIONS: This ARIES trial confirmed the activity and safety of avelumab for treating mUC, adding a new therapy option to the armamentarium of checkpoint inhibitors already approved for platinum-ineligible, locally advanced/mUC.

Sudden unexpected death in a 17-year-old boy due to unacknowledged adamantinoma-like Ewing sarcoma.

A 17-year-old male with no previous medical history was admitted 2 days before his death to a local hospital after mild dyspnea. Electrocardiography, chest radiography, and blood analysis revealed no abnormalities. Blood oxygen saturation was 99%, and SARS-CoV-2 nasopharyngeal swabs tested negative; thus, he was discharged without prescriptions. After 2 days, the subject died suddenly during a pool party. Forensic autopsy was performed analyzing all anatomical districts. Cardiac causes were fully excluded after deep macroscopic and microscopic evaluation; lung and brain analyses showed no macroscopic pathology. Finally, a large subglottic solid mass was detected. The whitish neoplasm showed an aggressive invasion pattern to the thyroid and adjacent deep soft tissues and occluded the trachea. High-power microscopy showed sheets of small, uniform cells with scant cytoplasm; round nuclei; and small, punctate nucleoli, with immunohistochemical expression of CK8-18, AE1/AE3, and CD99. Using FISH analysis, the break-apart molecular probes (EWSR1 (22q12) Break - XL, Leica Biosystem, Nussloch, Germany) showed distinct broken red and green fluorochromes, diagnostic of Ewing sarcoma. The neoplasm was characterized as adamantinoma-like Ewing sarcoma, and the mechanism of death was identified as airway obstruction. The rarity of the case resides in the circumstances of death, which pointed to the possibility of sudden unexpected death due to heart disease, but an oncological cause and the underlying mechanism were finally diagnosed. The best method to perform autopsies is still complete, extensive, and systematic macroscopic sampling of organs and districts followed by histopathological analysis, in addition to immunohistochemical and molecular investigations in those cases in which they are necessary. In fact, when neoplasms are detected, the application of advanced techniques such as immunohistochemistry and molecular diagnostics is fundamental to accurately certify death.

Learning effect and repeatability of stabilometric measurements: "standard" vs. usual foot placement.

The existence of a learning effect by which subjects progressively reduce body sway over the course of repetitive stabilometric measurements is currently debated. Also, the position and orientation of the feet on the platform can have a substantial influence on the outcome measurements. The aim of the present work was to assess the effect of feet positions on mean total velocity (V) of the center of pressure and the area (AR) covered by its displacements during quiet standing. A group of 35 healthy young subjects was examined during two successive sessions consisting of five recordings with their feet placed either in the recommended (standard, SP) or their usual most comfortable (UP) position. Results show a slight decreasing trend that failed to be statistically significant checked with Friedman's ANOVA (SP AR, χ2(4)=6.10, p=0.19 and V, χ2(4)=8.66, p=0.07 and UP AR, χ2(4)=2.32, p=0.68 and V, χ2(4)=1.19, p=0.88). Nonetheless, values of AR and V showed a notable decrement especially evident in the SP exam reaching, respectively, 24% and 11% from baseline, whereas variability measured by the coefficient of variation was the same in the two exams. Given the results, a learning effect should not be ruled out with confidence. Also, usual foot placement would be preferable to avoid this effect. Further research is needed to take into consideration the great variability of stabilometric measurements and the fact that different subjects could adapt more readily to the test conditions than others.

Changes of sensory and pain thresholds in healthy subjects after mandibular extension at maximum mouth opening: implications for temporomandibular disorders therapy.

There is evidence showing that increasing the vertical dimension of occlusion, or interocclusal distance, reduces pain symptoms in patients with temporomandibular disorders (TMD) and bruxism. The mechanism underlying the analgesic effect is still under investigation. Some researchers propose either a gate mechanism or the activation of the trigemino-cardiac reflex. In this study, sensory and pain thresholds changes in the mandibular district have been evaluated in twenty healthy subjects immediately after 5 minutes of mandibular stretching at maximum opening of the jaw. Results showed a 60% increment in sensory threshold and a 70% increment in pain threshold (p<0.001) compared with the baseline values. The magnitude of the analgesic effect seems proportional to the extent of mandibular opening. These and similar results are discussed as for the implication in the treatment of TMD related symptoms.

Stroke-like events after brain radiotherapy: a large series with long-term follow-up.

BACKGROUND AND PURPOSE: Patients with a history of brain radiotherapy can experience acute stroke-like syndromes related to the delayed effects of brain radiation, including stroke-like migraine attacks after radiation therapy syndrome, peri-ictal pseudoprogression and acute late-onset encephalopathy after radiation therapy syndrome. The aim of this study was to collect evidence on the long-term outcome and treatment of these conditions, whose knowledge is undermined by their rarity and fragmented description. METHODS: Cases were collected, both prospectively and retrospectively, amongst six neuro-oncology departments. Inclusion criteria were as follows: (i) history of brain radiotherapy (completed at least 6 months before the acute episode); (ii) new onset of acute/subacute neurological symptoms; (iii) exclusion of all etiologies unrelated to brain irradiation. A review of current literature on stroke-like syndromes was performed to corroborate our findings. RESULTS: Thirty-two patients with acute neurological conditions attributed to the delayed effects of radiation were identified, including 26 patients with stroke-like syndromes. Patients with stroke-like syndromes commonly presented with a mosaic of symptoms, including focal deficits (77%), encephalopathy (50%), seizures (35%) and headache (35%). Seventy-three percent of them had acute consistent magnetic resonance imaging alterations. Treatment included high-dose steroids in 65% of cases. Twenty-two patients recovered completely (85%). Sixteen patients (62%) experienced relapses (median follow-up 3.5 years). A literature review identified 87 additional stroke-like cases with similar characteristics. CONCLUSIONS: Stroke-like events related to brain irradiation may be associated with permanent sequelae. Steroids are often administered on empirical grounds, as they are thought to accelerate recovery. Relapses are common, highlighting the need to elaborate adequate prevention strategies.

An observational study of the effects of using an high oral splint on pain control

Increasing occlusal vertical dimension (OVD) by means of oral splints is a practice widely used in the treatment of temporomandibular disorders (TMD), specifically myofascial pain, although the results are still uncertain. Oral splints with a vertical height that significantly exceeds the clinical rest position are considered by some researchers to be a better therapeutic solution in alleviating TMD symptoms than are "low" splints. In our observational study, 21 patients suffering from myofascial pain were examined for the effects of wearing a "high" oral splint while sleeping for 3 months. To ensure proper splint making, a mandibular stretching procedure was used to induce a relaxation of the patients' masticatory muscles and allow the correct alignment of the jaws. Results showed a marked increase of the interocclusal distance or "free space" (hence of OVD; from 0.64±0.53 mm to 1.42±0.76 mm, p<0.0001) measured by a kinesiograph, followed by a substantial reduction of the intensity of pain in oral and extraoral regions after using the splint. These results support the view that increasing OVD beyond the clinical rest position is not detrimental to patients' health. More importantly, high oral splints has been shown to be a promising therapeutic aid for the treatment of TMD and correlated pain syndromes. This clinical trial was registered on clinicaltrials.gov (Identifier: NCT02908568).

Postural Disorders Produced by School Furniture on a Population of a Junior High School.

In recent years people suffering of backache has significantly increased. This led us to focus our attention on the adequacy of school furniture for the correct development of the adult posture. The standing posture of 67 students of middle school has been analyzed at the beginning and at the end of two consecutive scholastic years using a stabilometric platform. Starting from the second year, about half of the students were provided with the furniture designed following European standard (UNI EN 1729:2006), while the other half maintained the traditional one. The main purpose of this research has been to verify by means of posturometric analysis the effects on postural parameters of the use of traditional furniture in comparison to the furniture following the UNI EN 1729:2006. We observed that prolonged sitting at school changes some posturometric variables of schoolchildren. Since no differences has been found between the two groups, the validity of the European standards is questioned. The present study allowed us to single out four anthropometric parameters that should be considered in order to devise a new model of adjustable furniture. By adjusting every year the furniture of each student, it would be possible to avoid (at least at school) the adoption of wrong postural positions that could be responsible for backache and other common musculoskeletal disorders.

Experimental Determination of Irreversible Entropy Production in out-of-Equilibrium Mesoscopic Quantum Systems.

By making use of a recently proposed framework for the inference of thermodynamic irreversibility in bosonic quantum systems, we experimentally measure and characterize the entropy production rates in the nonequilibrium steady state of two different physical systems-a micromechanical resonator and a Bose-Einstein condensate-each coupled to a high finesse cavity and hence also subject to optical loss. Key features of our setups, such as the cooling of the mechanical resonator and signatures of a structural quantum phase transition in the condensate, are reflected in the entropy production rates. Our work demonstrates the possibility to explore irreversibility in driven mesoscopic quantum systems and paves the way to a systematic experimental assessment of entropy production beyond the microscopic limit.

ALK gene copy number gains in non-small-cell lung cancer: prognostic impact and clinico-pathological correlations.

BACKGROUND: The correlation between ALK gene copy number gain (ALK-CNG) and prognosis in the context of advanced non-small-cell lung cancer (NSCLC) remains a controversial issue. This study aimed to evaluate the association among ALK-CNG according to Fluorescent In Situ Hybridization (FISH), clinical characteristics and survival in resectable and advanced NSCLC. METHODS: Clinical and pathological data of patients with resectable and advanced NSCLC were retrospectively collected. Tumor tissues were analyzed for ALK-CNG by FISH, and patients were divided in 3 groups/patterns on the basis of ALK signals: disomic [Pattern A], 3-7 signals [Pattern B], >7 signals [Pattern C]. The association between clinical and pathological features and ALK-CNG patterns was evaluated. Disease/progression-free and overall survival (DFS/PFS and OS) were estimated using the Kaplan-Meyer method. RESULTS: A number of 128 (76.6 %) out of the 167 eligible patients were evaluable for ALK-CNG, displaying pattern A, B and C in 71 (42.5 %), 42 (25.1 %) and 15 (9 %) patients, respectively. Gains in ALK-CNG appear to be more frequent in smokers/former smokers than in non-smokers (74.2 % versus 20.4 %, respectively, p = 0.03). Pattern A and C seem more frequently associated with higher T-stage (T3-4), while pattern B appears more represented in lower T-stage (T 1-2) (p = 0.06). No significant differences in survival rate were observed among the above groups. CONCLUSIONS: A high ALK-CNG pattern might be associated with smoking status and theoretically it might mirror genomic instability. The implications for prognosis should be prospectively investigated and validated in larger patients' series. TRIAL REGISTRATION: We confirm that all the study was performed in accordance with relevant guidelines and regulations and that all the protocol (part of a larger project MFAG 2013 N.14282) was approved by the local Ethics Committee of the Azienda Ospedaliera Universitaria Integrata of Verona on November 11st, 2014.

Impact of HER2 copy number in IHC2+/FISH-amplified breast cancer on outcome of adjuvant trastuzumab treatment in a large UK cancer network.

BACKGROUND: Adjuvant trastuzumab with chemotherapy is standard treatment for HER2-positive breast cancer, defined as either HER2 IHC3+ or IHC2+ and FISH amplified. The aim of this study was to investigate the degree to which HER2 amplification in terms of HER2 gene copy numbers in HER2+IHC2+ cancers affected the outcome in a community setting. METHODS: Case records of 311 consecutive patients with early breast cancer presenting between 1st January 2005 and 31st December 2008 were reviewed. Progression-free survival and overall survival were calculated with the Kaplan-Meier method using STATA 13. RESULTS: Among 3+ cases (n=230) 163 received T vs 67 no-T. Among 2+ cases (n=81) 59 received T vs 22 no-T. Among 59 IHC2+-treated cases n=28 had an average of >12, n=13 had >6 to <12, and n=18 had >2 to <6 HER2 gene copies, respectively. The time of progression and overall survival of high and low copy number patients was similar and better than the intermediate copy number and the untreated cohorts. CONCLUSIONS: High HER2 copy number (>12) appears to be associated with consistently better response compared with patients with intermediate HER2 copy numbers (6-12). In light of emerging data of patients showing insensivity to trastuzumab therapy, we propose that the HER2 gene copy number value should be included as an additional indicator for stratifying both the management and the follow-up of breast cancer patients.

Atypical suicide by single incising cut to the throat without hesitation marks: Case report and review of the literature.

Several studies have been performed to recognize the main features in homicide and suicide sharp wound-related death, revealing that a single cutting wound to the neck is an infrequent event in suicide cases, and several hesitation marks near the fatal injury are usually present. We report a case of an atypical self-inflicted cutthroat injury without tentative marks involving a 79-year-old female. The weapon used, a kitchen knife, was found at the crime scene. The wound had clean margins, and no other incisions were found. Scene circumstances, namely the absence of signs of a break-in, the victim found on the bed, the knife located near the body, the vital wound in an accessible site, and the absence of defense injuries, collectively support a likely suicide. A literature review was also performed to compare forensic data of the case presented with the other 6 cases reported regarding atypical suicide characterized by a single incising cut to the throat without hesitation marks. Given the few cases reported and the lack of gross descriptions and histopathological data available in the literature, additional knowledge of such a case may help forensic pathologists in the identification of suicidal events when a single neck injury is observed. In this frame, suicide by a unique single incising cut to the throat without hesitation marks near the lethal injury may be observed as an atypical presentation, and the crime scene investigation, together with additional background information of the deceased, aid in the identification of the manner of the death.

A clinical-biological risk stratification model for resected gastric cancer: prognostic impact of Her2, Fhit, and APC expression status.

BACKGROUND: To obtain a prognostic stratification model for resected gastric cancer patients. PATIENTS AND METHODS: Clinicopathological and molecular data (expression of Cdx2, Apc, ß-catenin, E-cadherin, Fhit, p53, and human epidermal growth factor receptor-2 (Her2); HER2 and TOPO2A gene copy number; PIK3CA mutations; microsatellite instability) were correlated to cancer-specific/overall survival (CSS/OS) using a Cox model. Individual patient probability (IPP) was estimated by logistic equation. A continuous score to identify risk-classes was derived according to the model ratios. RESULTS: Two-hundred eight patients were studied (median follow-up 20 months). At multivariate analysis, sex, stage, margins, location, nodes, Apc, and Fhit were independent predictors for CSS; the same factors (and age and Her2, except Fhit) predicted OS. Multivariate model predicted IPP with high prognostic accuracy (0.90 for CSS; 0.91 for OS). A two-class model significantly separated low- and high-risk patients for CSS (23.4% and 85.6%, P < 0.0001) and OS (21.4% and 82.0%, P < 0.0001). A three-class model differentiated low-, intermediate-, and high-risk patients for CSS (6.3%, 35.3%, and 88.0%, P < 0.0001) and OS (6.1%, 34.6%, and 86.5%, P < 0.0001). CONCLUSIONS: A risk classification system comprising the immunohistochemical expression of three proteins (Apc, Fhit, and Her2) and five clinicopathological parameters (stage, resected nodes, margins, location, and sex) accurately separates the resected gastric cancer patients into three classes of risk.

Internet use in patients with cardiovascular diseases: Bad Berka Cross-Sectional Study (BABSY).

BACKGROUND: Internet has become a significant resource for dissemination of medical information. We sought to investigate prevalence and usage patterns of Internet access among consecutive patients with cardiovascular diseases. METHODS: A cross-sectional study was performed using a questionnaire as study tool. Among patients with Internet access, the type of health information sought and the impact of these on daily life were assessed. RESULTS: Of 1063 patients invited to the study, 1000 patients [68% male gender, mean age 66 ± 11 years (range 27-83 years)] agreed to complete the questionnaire. 216/1000 (21.6%) used Internet to obtain information related to their disease. The patient education was graded as: low (15%), medium (66%) and high (19%). Reasons for Internet use were as follows: 24-h availability 142/216 (65.7%); free of charge 58/216 (26.9%); and anonymity 50/216 (23.2%). Younger (≤ 66 years) age (35.2% vs. 15.3%; p = 0.0001), male gender (24.6% vs. 15.4%; p = 0.001) and higher education level (49.4% vs. 16.1%; p = 0.001) were significantly associated with Internet use. 30.6% (66/216) of Internet users changed their individual health behaviour attributable to information found on the Internet. However, this was not related to age, gender or level of education (p = 0.5, p = 0.6 and p = 0.4, respectively). Patients without Internet use obtain health information mainly from the pharmacist (62%) or from their treating physician (58%). CONCLUSIONS: A relevant number of patients with cardiovascular disease access the Internet for health information. The impact of such information on health-related behaviour in daily life was low.

Persistent effects after trigeminal nerve proprioceptive stimulation by mandibular extension on rat blood pressure, heart rate and pial microcirculation.

The trigemino-cardiac reflex is a brainstem reflex known to lead to a decrement in heart rate and blood pressure, whereas few data have been collected about its effects on the cerebral hemodynamic. In this study we assess the in vivo effects of trigeminal nerve peripheral stimulation by mandibular extension on pial microcirculation and systemic arterial blood pressure in rats. Experiments were performed in male Wistar rats subjected to mandibular extension obtained inserting an ad hoc developed retractor between the dental arches. Mean arterial blood pressure and heart rate were recorded and the pial arterioles were visualized by fluorescence microscopy to measure the vessel diameters before (15 minutes) during (5-15 minutes) and after (80 minutes) mandibular extension. While in control rats (sham-operated rats) and in rats subjected to the dissection of the trigeminal peripheral branches mean arterial blood pressure, heart rate and pial microcirculation did not change during the whole observation period (110 minutes), in rats submitted to mandibular extension, mean arterial blood pressure, heart rate and arteriolar diameter significantly decreased during stimulation. Afterward mean arterial blood pressure remained reduced as well as heart rate, while arteriolar diameter significantly increased evidencing a vasodilatation persisting for the whole remaining observation time. Therefore, trigeminal nerve proprioceptive stimulation appears to trigger specific mechanisms regulating systemic arterial blood pressure and pial microcirculation.

Pancreatic endocrine tumours: mutational and immunohistochemical survey of protein kinases reveals alterations in targetable kinases in cancer cell lines and rare primaries.

BACKGROUND: Kinases represent potential therapeutic targets in pancreatic endocrine tumours (PETs). PATIENTS AND METHODS: Thirty-five kinase genes were sequenced in 36 primary PETs and three PET cell lines: (i) 4 receptor tyrosine kinases (RTK), epithelial growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), tyrosine-protein kinase KIT (KIT), platelet-derived growth factor receptor alpha (PDGFRalpha); (ii) 6 belonging to the Akt/mTOR pathway; and (iii) 25 frequently mutated in cancers. The immunohistochemical expression of the four RTKs and the copy number of EGFR and HER2 were assessed in 140 PETs. RESULTS: Somatic mutations were found in KIT in one and ATM in two primary neoplasms. Among 140 PETs, EGFR was immunopositive in 18 (13%), HER2 in 3 (2%), KIT in 16 (11%), and PDGFRalpha in 135 (96%). HER2 amplification was found in 2/130 (1.5%) PETs. KIT membrane immunostaining was significantly associated with tumour aggressiveness and shorter patient survival. PET cell lines QGP1, CM and BON harboured mutations in FGFR3, FLT1/VEGFR1 and PIK3CA, respectively. CONCLUSIONS: Only rare PET cases, harbouring either HER2 amplification or KIT mutation, might benefit from targeted drugs. KIT membrane expression deserves further attention as a prognostic marker. ATM mutation is involved in a proportion of PET. The finding of specific mutations in PET cell lines renders these models useful for preclinical studies involving pathway-specific therapies.

[Increasing immunization coverage by intervening on determinants of refusal]. / Aumentare le coperture vaccinali intervenendo sui determinanti del rifiuto.

With the regional decree 3664/2008, the Veneto Region adopted measures for improvements in the immunization program, among which the "Investigation into determinants for vaccine refusal in the Veneto Region", entrusted by the Department of Prevention Local Health Unit 20 (Ulss 20) of Verona. The objective of the study was to understand which type of parent that accessed immunization services (total adherent, partial adherent or complete refusals) and what factors lead to their choice regarding immmunizations in order to better plan strategies to maintain vaccination coverage.

Outstation for x-ray powder diffraction at the Italian beamline at the European synchrotron.

LISA [Linea Italiana per la Spettroscopia di Assorbimento X, Italian beamline for X-ray Absorption Spectroscopy (XAS)] is the Italian CRG (Collaborating Research Group) beamline at the ESRF (European Synchrotron Radiation Facility) dedicated to XAS [d'Acapito et al., J. Synchrotron Radiat. 26, 551-558 (2019)]. In this work, a methodical test of the LISA beamline in performing diffraction measurements is carried out. Synchrotron x-ray diffraction measurements would complement absorption spectroscopy techniques with the long-range characterization of the material under investigation, while XAS provides the short-range element selective information.

Validation of the Meet-URO score in patients with metastatic renal cell carcinoma receiving first-line nivolumab and ipilimumab in the Italian Expanded Access Program.

BACKGROUND: The Meet-URO score allowed a more accurate prognostication than the International Metastatic RCC Database Consortium (IMDC) for patients with pre-treated metastatic renal cell carcinoma (mRCC) by adding the pre-treatment neutrophil-to-lymphocyte ratio and presence of bone metastases. MATERIALS AND METHODS: A post hoc analysis was carried out to validate the Meet-URO score on the overall survival (OS) of patients with IMDC intermediate-poor-risk mRCC treated with first-line nivolumab plus ipilimumab within the prospective Italian Expanded Access Programme (EAP). We additionally considered progression-free survival (PFS) and disease response rates. Harrell's c-index was calculated to compare the accuracy of survival prediction. RESULTS: Overall the EAP included 306 patients, with a median follow-up of 12.2 months, median OS was not reached, 1-year OS was 66.8% and median PFS was 7.9 months. By univariable analysis, both the IMDC score and the two additional variables of the Meet-URO score were associated with either OS or PFS (P < 0.001 for all comparisons). The four Meet-URO risk groups (G) had 1-year OS of 92%, 72%, 50% and 21% for G2 (29.1% of patients), G3 (28.8%), G4 (33.0%) and G5 (9.1%), respectively. OS was significantly shorter in each consecutive G (P = 0.001 for G3, P < 0.001 for both G4 and G5 compared to G2). Similarly, Meet-URO Gs 2-5 showed decreasing median PFS and response rates. The Meet-URO score showed the highest c-index for both OS (0.73) and PFS (0.67). Limitations include the post hoc nature of this analysis and the lack of a comparative arm to assess predictive value. CONCLUSION: The Meet-URO score appeared to show better prognostic classification than the IMDC alone in patients with mRCC at IMDC intermediate-poor risk treated with first-line nivolumab and ipilimumab.

Rietveld and pair distribution function study of Hägg carbide using synchrotron X-ray diffraction.

Fischer-Tropsch (FT) synthesis is an important process in the manufacturing of hydrocarbons and oxygenated hydrocarbons from mixtures of carbon monoxide and hydrogen (syngas). The reduced iron catalyst reacts with carbon monoxide and hydrogen to form bulk Fe(5)C(2) Hägg carbide (χ-HC) during FT synthesis. Arguably, χ-HC is the predominant catalyst phase present in the working iron catalyst. Deactivation of the working catalyst can be due to oxidation of χ-HC to iron oxide, a step-wise decarburization to cementite (θ-Fe(3)C), carbon formation or sintering with accompanying loss of catalytic performance. It is therefore critical to determine the precise crystal structure of χ-HC for the understanding of the synthesis process and for comparison with the first-principles ab initio modelling. Here the results of high-resolution synchrotron X-ray powder diffraction data are reported. The atomic arrangement of χ-HC was confirmed by Rietveld refinement and subsequent real-space modelling of the pair distribution function (PDF) obtained from direct Fourier transformation. The Rietveld and PDF results of χ-HC correspond well with that of a pseudo-monoclinic phase of space group Pi [a = 11.5661 (6) Å, b = 4.5709 (1) Å, c = 5.0611 (2) Å, α = 89.990 (5)°, ß = 97.753 (4)°, γ = 90.195 (4)°], where the Fe atoms are located in three distorted prismatic trigonal and one octahedral arrangement around the central C atoms. The Fe atoms are distorted from the prismatic trigonal arrangement in the monoclinic structure by the change in C atom location in the structure.