Diagnostic Utility of Genetic and Immunohistochemical H3-3A Mutation Analysis in Giant Cell Tumour of Bone

To validate the reliability and implementation of an objective diagnostic method for giant cell tumour of bone (GCTB). H3-3A gene mutation testing was performed using two different methods, Sanger sequencing and immunohistochemical (IHC) assays. A total of 214 patients, including 120 with GCTB and 94 with other giant cell-rich bone lesions, participated in the study. Sanger sequencing and IHC with anti-histone H3.3 G34W and G34V antibodies were performed on formalin-fixed, paraffin-embedded tissues, which were previously decalcified in EDTA if needed. The sensitivity and specificity of the molecular method was 100% (95% CI: 96.97–100%) and 100% (95% CI: 96.15–100%), respectively. The sensitivity and specificity of IHC was 94.32% (95% CI: 87.24–98.13%) and 100% (95% CI: 93.94–100.0%), respectively. P.G35 mutations were discovered in 2/9 (22.2%) secondary malignant GCTBs and 9/13 (69.2%) GCTB after denosumab treatment. We confirmed in a large series of patients that evaluation of H3-3A mutational status using direct sequencing is a reliable tool for diagnosing GCTB, and it should be incorporated into the diagnostic algorithm. Additionally, we discovered IHC can be used as a screening tool. Proper tissue processing and decalcification are necessary. The presence of the H3-3A mutation did not exclude malignant GCTB. Denosumab did not eradicate the neoplastic cell population of GCTB.

Metabolic switching and cell wall remodelling of Mycobacterium tuberculosis during bone tuberculosis

Bone tuberculosis is widely characterized by irreversible bone destruction caused by Mycobacterium tuberculosis . Mycobacterium has the ability to adapt to various environmental stresses by altering its transcriptome in order to establish infection in the host. Thus, it is of critical importance to understand the transcriptional profile of M. tuberculosis during infection in the bone environment compared to axenic cultures of exponentially growing M.tb. In the current study, we characterized the in vivo transcriptome of M. tuberculosis within abscesses or necrotic specimens obtained from patients with bone TB using whole genome microarrays in order to gain insight into the M. tuberculosis adaptive response within this host microenvironment. A total of 914 mycobacterial genes were found to be significantly over-expressed and 1688 were repressed (fold change>2; p-value ≤ 0.05) in human bone TB specimens. Overall, the mycobacteria displayed a hypometabolic state with significant (p ≤ 0.05) downregulation of major pathways involved in translational machinery, cellular and protein metabolism and response to hypoxia. However, significant enrichment (p ≤ 0.05) of amino-sugar metabolic processes, membrane glycolipid biosynthesis, amino acid biosynthesis (serine, glycine, arginine and cysteine) and accumulation of mycolyl-arabinogalactan-peptidoglycan complex suggests possible mycobacterial survival strategies within the bone lesions by strengthening its cell wall and cellular integrity. Data were also screened for M.tb virulence proteins using Virulent-Pred and VICM-Pred tools, which revealed five genes (Rv1046c, Rv1230c, DppD, PE_PGRS26 and PE_PGRS43) with a possible role in the pathogenesis of bone TB. Next, an osteoblast cell line model for bone TB was developed allowing for significant intracellular multiplication of M.tb. Interestingly, three virulence genes (Rv1046c, DppD and PE_PGRS26) identified from human bone TB microarray data were also found to be overexpressed by intracellular M. tuberculosis in osteoblast cell lines. Overall, these data demonstrate that M. tuberculosis alters its transcriptome as an adaptive strategy to survive in the host and establish infection in bone. Additionally, the in vitro osteoblast model we describe may facilitate our understanding of the pathogenesis of bone TB.

Neonatal osteofibrous dysplasia: Synchronous tibial and fibular involvement is common

Osteofibrous dysplasia is a rare non-malignant fibro-osseous bone tumour, first described and characterised under this name by Campanacci (1976). It is most commonly encountered in the tibia of children and young adults, but less frequently seen in the neonate with only few prior reports in the literature. We report a case of neonatal congenital osteofibrous dysplasia, presenting with unilateral limb deformity at birth. Radiographs demonstrated well-defined mixed lytic-sclerotic lesions, in a previously unreported distribution in this age-group, confined to the distal metadiaphysis of the affected tibia and fibula. Open surgery was performed for deformity correction, with tissue biopsy confirming the radiographically-suspected diagnosis. We present the up-to-date clinical, radiological, and pathological findings in this case of a rare pathology with some novel features, within this age group, in disease distribution and consequent radiographic appearances. OFD should be considered in the differential of similar congenital deforming bone lesions of the lower limb. We also review the small number of previously published cases of congenital OFD in the neonate, noting in particular that the frequency of ipsilateral fibular involvement appears to be higher than that observed in older patients.

Percutaneous CT-Guided Biopsy of the Craniovertebral Junction: Safety, Diagnostic Yield, and Technical Notes

The craniovertebral junction defined as the occiput, the atlas, and the axis is a complex bony region that contains vital neural and vascular structures. We report the experience of a single academic institution regarding CT-guided biopsy of this skeletal region. We reviewed all of the CT-guided biopsies performed in our department, completed in the craniovertebral junction. We collected data in regard to biopsy procedures, patients’ vital statistics, and histopathological diagnosis. In total, 16 patients (8M and 8F; mean age 52; range 16–86 years old) were included in this series. In eight patients, the lesions were located in the atlas vertebra (8/16—50%), in six patients in the axis (37.5%), and in two patients in the occiput (12.5%). No complications were observed during or after the procedures. All of the procedures were technically successful. The biopsy was diagnostic in 13/16 patients (81.3%): four metastatic lesions (25%—three breast and one prostate cancers), four multiple myeloma bone lesions (25%), three aneurismal bone cysts (18.8%), one aggressive hemangioma (6.3%), and one pseudogout (6.3%). Moreover, in two-thirds (66.6%) of non-diagnostic histological reports, malignancies were excluded. CT-guided percutaneous biopsy is a safe tool and allows obtaining a histological diagnosis, in most cases, even in the most delicate site of the human skeleton—the craniovertebral junction.

Correcting B0 inhomogeneity-induced distortions in whole-body diffusion MRI of bone

Diffusion-weighted magnetic resonance imaging (DWI) of the musculoskeletal system has various applications, including visualization of bone tumors. However, DWI acquired with echo-planar imaging is susceptible to distortions due to static magnetic field inhomogeneities. This study aimed to estimate spatial displacements of bone and to examine whether distortion corrected DWI images more accurately reflect underlying anatomy. Whole-body MRI data from 127 prostate cancer patients were analyzed. The reverse polarity gradient (RPG) technique was applied to DWI data to estimate voxel-level distortions and to produce a distortion corrected DWI dataset. First, an anatomic landmark analysis was conducted, in which corresponding vertebral landmarks on DWI and anatomic T2-weighted images were annotated. Changes in distance between DWI- and T2-defined landmarks (i.e., changes in error) after distortion correction were calculated. In secondary analyses, distortion estimates from RPG were used to assess spatial displacements of bone metastases. Lastly, changes in mutual information between DWI and T2-weighted images of bone metastases after distortion correction were calculated. Distortion correction reduced anatomic error of vertebral DWI up to 29 mm. Error reductions were consistent across subjects (Wilcoxon signed-rank p < 10–20). On average (± SD), participants’ largest error reduction was 11.8 mm (± 3.6). Mean (95% CI) displacement of bone lesions was 6.0 mm (95% CI 5.0–7.2); maximum displacement was 17.1 mm. Corrected diffusion images were more similar to structural MRI, as evidenced by consistent increases in mutual information (Wilcoxon signed-rank p < 10–12). These findings support the use of distortion correction techniques to improve localization of bone on DWI.

Case Report: Adult NTRK-Rearranged Spindle Cell Neoplasm: Early Tumor Shrinkage in a Case With Bone and Visceral Metastases Treated With Targeted Therapy

BackgroundNTRK (neurotrophic tyrosine receptor kinase)-rearranged spindle cell neoplasms are a new group of tumors included in the new 5th edition of the World Health Organization (WHO) classification of soft Tissue and Bone Sarcomas. These tumors are characterized by NTRK gene fusions and show a wide spectrum of histologies and clinical behavior. Several targeted therapies have recently been approved for tumors harboring NTRK fusions, including STS.Case PresentationA 26-year-old male with advanced, pretreated NTRK rearranged spindle cell neoplasm and liver, lung and bone metastases was treated with larotrectinib on a continuous 28-day schedule, at a dose of 100 mg twice daily. An 18FDG-PET/CT scan performed after 7 days of treatment showed tumor shrinkage in both visceral and bone lesions. There was no drug-related toxicity. Subsequent evaluations confirmed continued tumor regression in disease sites. The patient is well and continues treatment.ConclusionThe clinical and radiological response of our patient with an uncommon TPM4 (exon 7)-NTRK1 (exon 12) gene fusion tumor treated with a first-generation TRK inhibitor could contribute to a better understanding of the biology of this new STS entity and help to improve patient management.

Changing Threshold-Based Segmentation Has No Relevant Impact on Semi-Quantification in the Context of Structured Reporting for PSMA-PET/CT

Prostate-specific membrane antigen (PSMA)-directed positron emission tomography/computed tomography (PET/CT) is increasingly utilized for staging of men with prostate cancer (PC). To increase interpretive certainty, the standardized PSMA reporting and data system (RADS) has been proposed. Using PSMA-RADS, we characterized lesions in 18 patients imaged with 18F-PSMA-1007 PET/CT for primary staging and determined the stability of semi-quantitative parameters. Six hundred twenty-three lesions were categorized according to PSMA-RADS and manually segmented. In this context, PSMA-RADS-3A (soft-tissue) or -3B (bone) lesions are defined as being indeterminate for the presence of PC. For PMSA-RADS-4 and -5 lesions; however, PC is highly likely or almost certainly present [with further distinction based on absence (PSMA-RADS-4) or presence (PSMA-RADS-5) of correlative findings on CT]. Standardized uptake values (SUVmax, SUVpeak, SUVmean) were recorded, and volumetric parameters [PSMA-derived tumor volume (PSMA-TV); total lesion PSMA (TL-PSMA)] were determined using different maximum intensity thresholds (MIT) (40 vs. 45 vs. 50%). SUVmax was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories (p ≤ 0.0322). In particular, the clinically challenging PSMA-RADS-3A lesions showed significantly lower SUVmax and SUVpeak compared to the entire PSMA-RADS-4 or -5 cohort (p < 0.0001), while for PSMA-RADS-3B this only applies when compared to the entire PSMA-RADS-5 cohort (p < 0.0001), but not to the PSMA-RADS-4 cohort (SUVmax, p = 0.07; SUVpeak, p = 0.08). SUVmean (p = 0.30) and TL-PSMA (p = 0.16) in PSMA-RADS-5 lesions were not influenced by changing the MIT, while PSMA-TV showed significant differences when comparing 40 vs. 50% MIT (p = 0.0066), which was driven by lymph nodes (p = 0.0239), but not bone lesions (p = 0.15). SUVmax was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories in 18F-PSMA-1007 PET/CT. As such, the latter parameter may assist the interpreting molecular imaging specialist in assigning the correct PSMA-RADS score to sites of disease, thereby increasing diagnostic certainty. In addition, changes of the MIT in PSMA-RADS-5 lesions had no significant impact on SUVmean and TL-PSMA in contrast to PSMA-TV.

Amino Acid and Proliferation PET/CT for the Diagnosis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by infiltration of monoclonal plasma cells in the bone marrow (BM). The standard examination performed for the assessment of bone lesions has progressed from radiographic skeletal survey to the more advanced imaging modalities of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT). The Durie–Salmon PLUS staging system (upgraded from the Durie–Salmon staging system) applies 2-[18F]-fluoro-2-deoxy-glucose (18F-FDG) PET/CT, and MRI findings to the staging of MM, and 18F-FDG PET/CT has been incorporated into the International Myeloma Working Group (IMWG) guidelines for the diagnosis and staging of MM. However, 18F-FDG PET/CT has significant limitations in the assessment of diffuse BM infiltration and in the differentiation of MM lesions from inflammatory or infectious lesions. The potential of several new PET tracers that exploit the underlying disease mechanism of MM has been evaluated in terms of improving the diagnosis. L-type amino acid transporter 1 (LAT1), a membrane protein that transports neutral amino acids, is associated with cell proliferation and has strong ability to represent the status of MM. This review evaluates the potential of amino acid and proliferation PET tracers for diagnosis and compares the characteristics and accuracy of non-FDG tracers in the management of patients with MM.

Quantitative Analysis of SPECT-CT Data in Metastatic Breast Cancer Patients—The Clinical Significance

Purpose: To assess the potential added value of the SPECT-CT quantitative analysis in metastatic breast cancer lesions detection and differentiation from degenerative lesions. Methods: This prospective monocentric study was conducted on 70 female patients who underwent SPECT-CT bone scans using 99mTc–HDP that identified the presence of metastatic bone lesions and degenerative lesions in each patient. Once the lesions were identified, a quantitative analysis of radiotracer uptake was conducted. The highest one to five SUVmax values for both metastatic and degenerative bone lesions were identified in each patient and the data were then statistically analyzed. Results: The SUVmax value was significantly higher in metastatic bone lesions than in degenerative lesions (p < 0.001). The diagnostic accuracy of SPECT-CT quantitative data analysis revealed a sensitivity of 91.5% and a specificity of 93.3% at a cut-off value of the SUVmax of 16.6 g/mL. Conclusion: Quantitative analysis performed using SPECT-CT data can improve the diagnostic accuracy in differentiating between metastatic bone lesions and degenerative lesions, thus leading to appropriate treatment and better follow-up in metastatic breast cancer patients.