The use of the flow-void sign on MRI: highly sensitive sign in detecting bone metastases from renal cell carcinoma.

OBJECTIVE: To evaluate a range of pathologically proven malignant bone tumours, including primary bone sarcoma and metastatic bone lesions, referred to a tertiary referral centre for the presence of the flow-void sign on MR imaging. MATERIALS AND METHODS: A retrospective search was performed using the radiology information system and oncology database in our institution to identify patients over the age of 40 years referred with a solitary bone lesion. Patients with a range of pathologically proven malignant bone tumours, including primary bone tumours and metastatic bone lesions, were included in the study. MRI images were reviewed for the presence of the flow-void sign. The presence and type of the flow-void sign were correlated with lesion size. RESULTS: Two hundred and sixty-six cases were included in the study. Overall, the flow-void sign was identified in 40.9% of cases. The flow-void sign was most frequently seen in renal cell carcinoma metastasis (90.0%). The sign is highly sensitive (90%) for renal cell carcinoma metastases with a high negative predictive value (98.09%). When the flow-void sign is identified, the lesion is almost three times more likely to represent a renal cell carcinoma metastasis than any other malignant tumour in patients over the age of 40 years with a solitary bone lesion. CONCLUSION: The flow-void sign is highly sensitive for renal cell carcinoma bone metastases and could negate the need for biopsy in patients with a known history of renal cell carcinoma or in whom an occult renal cell carcinoma is subsequently identified.

Normal Bone Marrow and Non-neoplastic Systemic Hematopoietic Disorders in the Adult.

This article provides an overview of the imaging appearances of normal adult bone marrow with an emphasis on magnetic resonance imaging. We also review the cellular processes and imaging features of normal developmental yellow-to-red marrow conversion and compensatory physiologic or pathologic red marrow reconversion. Key imaging features that differentiate between normal adult marrow, normal variants, non-neoplastic hematopoietic disorders, and malignant marrow disease are discussed, as well as posttreatment changes.

Imaging of bone and soft tissue BCOR-rearranged sarcoma.

With recent advances in molecular research, an ever-increasing number of undifferentiated round cell sarcomas without the characteristic gene fusions of Ewing sarcoma are being discovered. One specific subtype termed BCOR-rearranged sarcoma belongs to this group. Previously termed 'Ewing-like' sarcoma, it was formally included with undifferentiated round cell tumours in the 2013 WHO Classification of Soft Tissue and Bone Tumours. However, in the 2020 WHO Classification, BCOR-sarcoma is now recognized as a distinct entity due to particular morphological and immunohistochemical features and differing clinical outcomes. As with classical Ewing sarcoma, osseous BCOR-rearranged sarcoma is an aggressive tumour with a similar clinical presentation. However, there are only a small handful of case series and isolated reports detailing the imaging characteristics, typically demonstrating an aggressive bone lesion with a large soft tissue mass. Soft tissue BCOR-sarcoma is even rarer. The aim of the current review is to describe the patient demographics, lesion locations and various imaging characteristics of histologically proven cases of musculoskeletal bone and soft tissue BCOR-sarcoma as described in the literature.

An accessory iliotibial band insertion: a unique anatomical variant.

The iliotibial band (ITB) is considered an important anterolateral knee joint stabiliser. Its exact anatomy remains unclear with inconsistency owing to relative paucity of detailed cadaveric studies. Multiple ITB distal insertional sites have been reported, the most common and well known being a direct attachment onto Gerdy's tubercle of the anterolateral tibia. We report a rare distal insertional site not previously documented. A 50-year-old man presented with anterior knee pain. MRI showed an accessory band deep to the ITB, partially blending in with its superficial fibres. It inserted onto the anterolateral tibial tuberosity, deep to the patellar tendon insertion and inferomedial to Gerdy's tubercle. This was asymptomatic but the patient did have an underlying median patella ridge osteochondral defect successfully treated with stem cell grafting, completely unrelated to the mentioned variant. This case highlights the importance of detecting rare anatomical variants which can potentially be a source of lateral knee pain.

Musculoskeletal imaging features of non-Langerhans cell histiocytoses.

The non-Langerhans cell histiocytoses (N-LCH) represent a group of rare diseases with different clinical presentations and imaging features to classical LCH. While there is a long list of entities, only few present with musculoskeletal soft tissue and osseous manifestations alongside the more commonly reported systemic findings. Erdheim-Chester disease (ECD) is typically seen in adults as bilateral and symmetrical long bone osteosclerosis. Rosai-Dorfman disease (RDD) is more commonly seen in children and young adults with bone involvement usually being a manifestation of extra-nodal disease. Primary osseous RDD is very rare, with both displaying rather non-specific imaging features of an expansile lucent lesion with or without an extra-osseous component. Juvenile xanthogranuloma (JXG) is a benign disorder typically seen in very young children. The most common imaging manifestation is a dermal or sub-dermal soft tissue mass. This article reviews the musculoskeletal imaging appearances of the commoner N-LCH.

Skeletal staging in Langerhans cell histiocytosis: a multimodality imaging review.

Evaluating the extent of skeletal disease in Langerhans cell histiocytosis (LCH) is a major predictor of patient outcome. Traditionally, whole-body skeletal staging consists of plain radiography and bone scintigraphy. However, more recently whole-body MRI has been shown to be accurate in detecting osseous and extra-osseous lesions, but no large-scale studies analysing its role within the diagnostic algorithm of LCH skeletal staging currently exist. In addition, FDG PET-CT provides useful information regarding disease activity and treatment response, but has an inherent radiation dose which is not ideal in children. Currently, radiographic skeletal survey remains the gold standard with cross-sectional imaging only performed for further characterisation. However, radiographs have shown a wide sensitivity range for skeletal staging and have clear limitations in detecting extra-skeletal disease, a crucial component of stratification in identifying 'at risk' organs. We aim to highlight the various appearances of bony LCH across all the imaging modalities for primary skeletal staging. We will also review the advantages, disadvantages, sensitivity and specificity of each, and establish their role in staging skeletal LCH. Recent studies using whole-body MRI have shown promising results, with radiographs and other modalities playing a more complementary role.

MRI features of low-grade and high-grade chondrosarcoma in enchondromatosis.

OBJECTIVE: To identify magnetic resonance imaging (MRI) features which aid differentiation of low-grade chondral tumours (LGCT-enchondroma and grade 1 chondrosarcoma) from high-grade chondral tumours (HGCT) in patients with enchondromatosis. MATERIALS AND METHOD: Approval from our local Research and Innovation Centre of The Institute of Orthopaedics was gained. Patients with enchondromatosis who had biopsy and/or resection of chondral lesions over a 13-year period were identified. The pre-biopsy MRI study was assessed by two experienced musculoskeletal radiologists for tumour origin (intramedullary or surface), cortical expansion, cortical destruction, bone marrow oedema, periosteal reaction, soft tissue mass and soft tissue oedema. MRI features were compared with the final histopathological diagnosis. RESULTS: The study group comprised 25 males and 16 females, with a mean age of 34.9 years (range 6-81 years). Fifty-nine lesions were assessed (12 patients had > 1 tumour treated), including 43 LGCT and 16 HGCT. Significant MRI features suggesting malignant transformation to HGCT for both observers included bone oedema (p = < 0.001 and 0.002), periosteal reaction (p = 0.01) and soft tissue oedema (p = 0.001 and 0.05). Cortical destruction and soft tissue mass were predictors of HGCT in major long bones, but no significant differentiating features were identified in the hands and feet. CONCLUSION: The presence of bone oedema, periosteal reaction and soft tissue oedema on MRI may indicate a high-grade malignant transformation of chondral tumours in patients with enchondromatosis.

Magnetic resonance imaging of trunk and extremity myxoid liposarcoma: diagnosis, staging, and response to treatment.

Myxoid liposarcoma (MLS) accounts for approximately 30% of all liposarcomas. The majority are intermediate-grade tumours, but the presence of >5% round cell component renders it a high-grade sarcoma with subsequent poorer outcome. MLS most commonly arises in the lower extremities, has a predilection for extra-pulmonary sites of metastatic disease, and is recognized to be radiosensitive. The purpose of the current article is to review the role of MRI in the management of MLS, including the characteristic features of the primary tumour, features which help to identify a round cell component and thus determine prognosis, the role of whole-body MRI for evaluation of extra-pulmonary metastatic disease, and the utility of MRI for assessing treatment response. The MRI differential diagnosis of MLS is also considered.

Introducing image-guided synovial aspiration and biopsy in assessing peri-prosthetic joint infection: an early single-centre experience.

AIM: Synovial sampling can be used in the diagnosis of peri-prosthetic joint infection (PJI). The purpose of this study was to establish the role of simultaneous image-guided synovial aspiration and biopsy (SAB) during an initial 2-year experience at our institution. METHODS: Retrospective review of consecutive SABs performed during 2014-2016 at a tertiary referral musculoskeletal centre. Radiological SAB microbiology culture results were compared with intra-operative surgical samples or multidisciplinary team (MDT) meeting outcome at 1-year follow-up if surgery was not undertaken. Sensitivity, specificity and accuracy of synovial aspiration (SA), synovial biopsy (SB) and simultaneous SAB were calculated. RESULTS: 103 patients (46 male, 57 female) totalling 111 procedures were analysed with mean age 65 years (range 31-83). Image-guided synovial procedures were performed on 52 (46.9%) hip and 59 (53.1%) knee joint prostheses. The mean combined sensitivity, specificity and accuracy for the entire cohort was 72.6%, 96.9% and 90%, respectively. When only SB was obtained, diagnostic accuracy (92.5%) was similar to SA alone (94.1%). In total, there were 21 (18.9%) true-positive, 80 (72.1%) true-negative, 2 (1.8%) false-positive and 8 (7.2%) false-negative cases (PPV 91.3% and NPV 90.9%). No post-procedural complications were recorded at 1-year follow-up. CONCLUSION: Percutaneous image-guided SAB is a valuable technique in assessing suspected PJI, with most samples indicative of infective status and causative organisms when validated against intra-operative results and specialist MDT evaluation. Image-guided SB is a safe and useful additional procedure following failed SA with equivalent levels of diagnostic accuracy.

Chondral tumours: discrepancy rate between needle biopsy and surgical histology.

OBJECTIVE: To determine the reliability of image-guided core needle biopsy (IGCNB) for the diagnosis and grading of chondral tumours of bone compared with surgical histology. MATERIALS AND METHODS: Retrospective review of patients with a chondral tumour of bone who underwent IGCNB and surgical resection between January 2007 and December 2017. Data collected included age, sex, skeletal location, technique used for IGCNB, IGCNB result including histological grade and comparison with surgical histology. RESULTS: A total of 237 patients were included (135 males and 102 females with mean age 53.7 years, range 9-89 years). A total of 174 IGCNBs were CT-guided, 57 ultrasound-guided and 6 fluoroscopic-guided. Two hundred thirty-six of 237 (99.6%) IGCNBs were diagnostic for a chondral tumour, although grade could not be determined in 13 (5.5%) due to necrosis. A positive correlation for tumour grade between IGCNB and surgical histology was achieved in 181 cases (76.4%). In 36 patients (15.2%), IGCNB under-graded the tumour, while in 6 (2.5%), IGCNB over-graded the tumour. Discrepancy between IGCNB and surgical histology was significantly greater for surface/peripheral lesions (p = 0.02) and lesions arising from the flat bones or spine (p = 0.002). DISCUSSION: IGCNB can achieve a diagnosis of a chondral tumour in a high proportion of cases when compared with final diagnosis from surgical resection specimens. However, correlation of tumour grade between IGCNB and resection histology is less reliable with discordance seen in almost one-quarter of cases, most commonly at non-appendicular sites. Therefore, IGCNB results should not be considered in isolation of imaging and clinical features when planning surgical management.