Neoplastic and non-neoplastic lesions occur commonly in the bones of the knee. For certain tumours, it is the most frequent location, and it is also a common site for neoplasms and non-neoplastic tumour mimics that do not demonstrate a particular anatomic preference. Lesions may arise at the end of the bone (subarticular) or in the metaphysis and extend towards the joint. Tumours and tumour mimics occurring in subarticular locations or extending from the metaphysis are considered separately in this review. We have included lesions that we expect will be identifiable on routine knee MRI examinations.

BACKGROUND:Chondrosarcomas are primary bone malignancies, with most lesions of the hand representing low grade chondral tumours (LGCT). Low grade (grade one) chondrosarcomas are defined as Atypical Cartilaginous Tumours by the 2020 World Health Organisation Classification. Grades two and three are termed high-grade chondral tumours (HGCT). AIM:To establish whether low-grade chondral tumours of the hand can be safely treated with simple curettage and assess recurrence rates. METHODS:Retrospective data was analysed from a tertiary referral hospital for bone tumours in the UK over a 13-year period. 158 patients with histological proven chondral tumours of the hand, requiring curettage, resection or amputation were included. RESULTS:13 (8.2%) had HGCT and 145 (91.8%) had LGCT. 136 LGCTs underwent intralesional curettage (98.5%). 8 (5.1%) underwent wide local resection (6 LGCT and 2 HGCT). 14 (8.9%) underwent amputation (5 LGCT and 9 HGCT). All HGCT patients were free from recurrence at a median of 81.7 months. Patients expressing GD2/3 tumour marker antigens were more likely to be HGCT on histology compared with those not expressing GD2/3 and more likely to require extensive surgery. CONCLUSION:In contrast to chondrosarcoma occurring in long bones, there is often discordance between histological and radiological appearance in lesions occurring in the small bones of the hand. These lesions may appear aggressive radiologically but prove to be low-grade on histology. We concluded that intralesional curettage was an effective method for managing LGCT of the hand, whilst more extensive surgery can be reserved for higher grade tumours. GD2/3 expression was associated with high-grade lesions. EVIDENCE LEVEL:III.

To assess the yield and clinical impact of image-guided bone biopsy for osteomyelitis of the appendicular skeleton. A literature search of several databases was conducted from inception to August 2023. Eligible studies reported patients who underwent image-guided bone biopsy for investigation of osteomyelitis of the appendicular skeleton. The pooled proportions were analyzed using a random-effects model. This review was registered in PROSPERO (CRD42023466419). From 370 initial studies screened, eight met the eligibility criteria, with a total of 700 patients. The pooled technical success rate was 99.6

Objective: The aim of this study is to determine MRI features that may be prognostic indicators of local recurrence (LR) in patients treated with curettage and cementation of atypical cartilaginous tumours (ACTs) in the appendicular skeleton. Materials and Methods: This study is a retrospective review of adult patients with histologically confirmed appendicular ACT. The data collected included age, sex, skeletal location and histology from curettage, the presence of LR and oncological outcomes. The pre-operative MRI characteristics of the ACT reviewed by a specialist MSK radiologist included lesion location, lesion length, degree of medullary filling, bone expansion, cortical status and the presence of soft tissue extension. Results: A total of 43 patients were included, including 9 males and 34 females with a mean age of 42.8 years (range: 25–76 years). Tumours were located in the femur (n = 19), humerus (n = 15), tibia (n = 5), fibula (n = 2) and radius and ulna (n = 1 each). A total of 19 lesions were located in the diaphysis, 12 in the metadiaphysis, 6 in the metaphysis and 6 in the epiphysis. The mean tumour length was 61.0 mm (range: 12–134 mm). The mean follow up was 97.7 months (range: 20–157 months), during which 10 (23.3%) patients developed LR, 7 (70%) of which were asymptomatic and 3 (30%) of which presented with pain. Four patients required repeat surgery with no associated death or evidence of metastatic disease. LR was significantly commoner with tumours arising in the epiphysis or metadiaphysis, but no MRI features were predictive of LR. Conclusions: No relationship was found between the apparent ‘aggressiveness’ of an ACT of the appendicular skeleton on MRI and the development of LR following treatment with curettage and cementation.

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. 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. 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. 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.

Objectives: To determine the incidence of pulmonary metastases on chest CT in trunk and extremity soft tissue sarcoma based on two size criteria, and to identify factors associated with metastases. Methods: Retrospective review of chest CT studies in patients with trunk and extremity soft tissue sarcoma over an 18-month period. Data collected included patient age/sex, tumour location, size and relationship to fascia. All chest CTs were reviewed for the presence of metastases which were diagnosed according to two size criteria: multiple nodules > 5mm in size or multiple nodules > 10 mm in size. Follow-up CT studies were reviewed in cases initially considered indeterminate. Results: 127 males and 73 females were included (mean age 57.1 years; range 10-90 years). 147 (73.5%) tumours were deep to the fascia and 53 (26.5%) superficial. Tumour size classified according to the 12 AJCC 2019 criteria was: T1 = 52, T2 = 76, T3 = 39, T4 = 33. Based on nodule size >5mm, 73 (36.5%) patients had no metastases, 42 (21%) had metastases, while 85 (42.5%) studies were indeterminate. Based on nodule size >10mm, 73 (36.5%) patients had no metastases, 28 (14%) had metastases, while 99 (49.5%) studies were indeterminate. Larger maximum dimension of the primary tumour was a risk factor for pulmonary metastases using both size criteria. Conclusion: The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14-21%. 42.5-49.5% of chest CTs were indeterminate. Advances in knowledge: The incidence of pulmonary metastases at presentation in trunk and extremity soft tissue sarcoma is 14-21%. Indeterminate pulmonary nodules are also very common.

Objectives: To compare the grading of lumbar degenerative disc disease (DDD), Modic end-plate changes (MEPC) and identification of high intensity zones (HIZ) on a combination of sagittal T 1weighted turbo spin echo (T 1W TSE), T 2weighted fast spin echo (T 2W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T 2W FSE Dixon MRI sequence which provides in-phase, opposed-phase, water only and fat only images in a single acquisition (Dixon protocol). Methods: 50 patients underwent lumbar spine MRI using the routine protocol with the addition of a T 2W FSE Dixon sequence. DDD grade, MEPC and HIZ for each disc level were assessed on the routine and Dixon protocols. Each protocol was reviewed independently by three readers (consultant musculoskeletal radiologists with 26-, 8- and 4 years’ experience), allowing assessment of inter-reader agreement and inter protocol agreement for each assessed variable. Results: The study included 17 males and 33 females (mean age 51 years; range 8–82 years). Inter-reader agreement for DDD grade on the routine protocol was 0.57 and for the Dixon protocol was 0.63 (p = 0.08). Inter-reader agreement for MEPC on the routine protocol was 0.45 and for the Dixon protocol was 0.53 (p = 0.02), and inter-reader agreement for identification of the HIZ on the routine protocol was 0.52 and for the Dixon protocol was 0.46 (p = 0.27). Intersequence agreement for DDD grade ranged from 0.61 to 0.97, for MEPC 0.46–0.62 and for HIZ 0.39–0.5. Conclusion: A single sagittal T 2W FSE Dixon MRI sequence could potentially replace the routine three sagittal sequence protocol for assessment of lumbar DDD, MEPC and HIZ resulting in ~60% time saving. Advances in knowledge: Grading of lumbar DDD, presence of Modic changes and high intensity zones were compared on sagittal T 1W TSE, T 2W FSE and STIR sequences with a T 2W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.

Study design Retrospective cohort study. Objective The cervical high-intensity intramedullary (CHII) lesion is a recognised finding in achondroplasia, manifesting as a focal area of increased T2W signal intensity in the upper cervical cord in the absence of cervical cord compression. The aim of this study is to determine the natural history of this abnormality. Setting Tertiary referral spinal and orthopaedic hospital, UK. Methods A retrospective review was undertaken of all patients with achondroplasia who had undergone at least one MRI study which included the cervical spine. Patient age at presentation was recorded and presence of the CHII lesion was determined on the sagittal T2W FSE sequence. For patients who had follow-up studies, presence of the CHII lesion was assessed for any change in morphology (resolution, partial resolution or enlargement). The development of new CHII lesions and presence of associated cord atrophy was also recorded. Results The study group consisted of 40 patients (20 males, 20 females: mean age at first MRI of 32.6 years (range 7-66 years). The CHII lesion was identified in 19 (47.5%) cases and was associated with focal cord atrophy in 17 (85%) cases. There was no change or resolution of these lesions nor any associated cord compression. No new CHII lesions developed but progressive cord atrophy was evident. Conclusion The CHII lesion is seen in 47.5% of cases of achondroplasia. It appears to be a stable abnormality which does not progress or change its morphology. However, it does appear to be associated with progressive cord atrophy.

OBJECTIVE:To determine the incidence and causes of pathological fractures in paediatric bone tumours and tumour-like lesions, and to determine if they are predictive of benign lesions.METHODS AND MATERIALS:Retrospective review of children with suspected bone tumours referred to a specialist musculoskeletal oncology service between September 2019 and August 2020. Data recorded included patient age and gender, lesion location, the presence of a pathological fracture on the initial plain radiograph, and the final diagnosis made either by image-guided biopsy/curettage or based on typical imaging features.RESULTS:231 patients were included with 233 lesions (138 males and 93 females with mean age 10.5 years, range 3 months-18 years). Final diagnosis was based on histology in 85 (36.5%) cases and imaging in 148 (63.5%) cases, 52 (22.3%) lesions classed as non-neoplastic, 139 (59.7%) as benign and 42 (18%) as malignant. Pathological fractures were seen in 41 cases (17.6%) at presentation, involving the humerus in 19 (46.3%), the femur in 14 (34.1%), the tibia in 3 (7.3%), the fibula and radius in two each (4.9%) and the second toe proximal phalanx in 1 (2.4%) (p < 0.001). The commonest underlying lesions included simple bone cyst (n = 17; 41.5%) and non-ossifying fibroma (n = 10; 24.4%). Only 4 cases (9.75%) were malignant, one case each of osteosarcoma, Ewing sarcoma, leukaemia and BCOR undifferentiated round cell sarcoma. Pathological fracture occurred in 27.7% of non-malignant lesions and 9.5% of malignant lesions, this difference being statistically significant (p < 0.001).CONCLUSION:Pathological fractures were seen in 17.6% of paediatric bone tumours, tumour-like lesions, being significantly associated with humeral location and non-malignant diagnosis.ADVANCES IN KNOWLEDGE:Demonstrates the frequency, location and underlying diagnosis of pathological fractures in paediatric bone tumour and tumour-like lesions.

Approximately 40% of conventional chondrosarcomas arise from the shoulder girdle, chest wall and pelvis. This pictorial review describes the MRI features which may aid in the differentiation of Grade 1 chondrosarcoma (Gd1-CS) from high-grade chondrosarcoma (HG-CS) and dedifferentiated chondrosarcoma (DD-CS) in these locations, based on literature review and assessment of 111 consecutive cases presenting to the senior authors institution over a 13-year period. Of the 111 patients reviewed (71 males and 40 females; mean age 54.3 years; range 17-92 years), 27 were Gd1-CS, 72 were HG-CS and 12 were DD-CS. Tumours arising from the scapula, acetabulum, pubis/ischium and sacrum were more likely to be HG-CS, as were intramedullary tumours. MRI features associated with HG-CS and DD-CS included cortical destruction, bone oedema, soft tissue oedema, tumour necrosis, intermediate T2W SI and joint invasion. The presence of a soft tissue mass became a significant differentiating feature for tumours arising within the medullary cavity, but this was location-specific and did not differentiate between Gd1-CS and HG-CS/DD-CS arising from the sternum or clavicle.

Objectives: To determine the differential diagnosis of dermal and sub-dermal soft tissue masses which do not extend to the deep fascia that are referred to a specialist musculoskeletal oncology service. Materials and methods: Review of all patients referred to a specialist musculoskeletal oncology service over a 13month period with a dermal or sub-dermal soft tissue mass which did not extend to the deep fascia based on MRI appearances. Data collected included age, gender, site and maximal lesion size, and final histological diagnosis for biopsied and/or excised lesions. Results: 56 patients were included, 21 (37.5%) males and 35 (62.5%) females with mean age 49.75 years (range 5-86 years). 3 patients had 2 lesions making a total of 59 lesions, 11 (18.6%) dermal and 48 (81.4%) sub-dermal. Histological diagnosis was available in 44 (74.6%) cases, of which 11 (25%) were non-neoplastic, 23 (52.3%) were benign neoplasms, and 10 (22.7%) were malignant neoplasms. Although older age at presentation and greater mean maximal tumour dimension were seen with malignant lesions, these did not reach statistical significance (p = 0.154 and 0.102 respectively). There was also no relationship between skin involvement from subdermal lesions and malignancy, but 5 of 6 dermal lesions which showed an exophytic growth pattern were malignant. Conclusions: The differential diagnosis of dermal and sub-dermal lesions which do not reach the deep fascia is wide with a malignant lesion being the cause in almost one-quarter of cases.

Most of the accessory muscles of the forearm described in the radiology literature are located either in the radial aspect of the forearm or towards the hypothenar eminence. We present an unusual case of an ulnar-sided distal forearm accessory flexor carpi ulnaris muscle presenting as a “pseudotumour“ demonstrated with both ultrasound and MRI, rarely reported in the current surgical and anatomical literature. Given the location and relation to the ulnar nerve towards Guyon’s canal, the accessory muscle may also predispose to distal ulnar nerve entrapment.

Dermatofibrosarcoma protuberans (DFSP) is an intermediate-grade tumour which may undergo fibrosarcomatous transformation to a high-grade sarcoma (DFSP-FST). DFSP-FST requires wide local resection, and therefore, pre-operative identification is important. The aims of this study are to see if DFSP and DFSP-FST can be differentiated based on MRI appearances, and to determine the ability of ultrasound-guided core needle biopsy (US-CNB) to identify DFSP-FST. Retrospective review of patients with a histological diagnosis of DFSP with/without transformation to DFSP-FST. Patient age, gender, lesion location and maximal size were recorded, as were several MRI features. MRI studies were reviewed independently by 2 musculoskeletal radiologists and the assessed features were then compared with final surgical resection histology. Histological results of US-CNB were also compared with final surgical pathology. A total of 42 patients were included, 26 males and 16 females with a mean age of 41.3 years (range 3–78 years). The upper limb was involved in 12 cases, the lower limb in 17 and the trunk in 13. Final surgical histological diagnosis was DFSP in 21 (50%) cases and DFSP-FST in 21 (50%) cases. Mean tumour dimension for DFSP was 32 mm and DFSP-FST 68 mm (p < 0.001). MRI features indicative of DFSP-FST included multi-lobular morphology (p = 0.03), T2W hypointensity compared with fat (p = 0.03), internal flow voids (p = 0.03) and peri-tumoral oedema (p < 0.001). Only 3 cases of DFSP-FST were correctly diagnosed on US-CNB. Various MRI findings can suggest a diagnosis of DFSP-FST, but US-CNB is unreliable at identifying high-grade fibrosarcomatous transformation.

Objective: Chemical shift artefact (CSA) is often encountered during MRI evaluation of superficial soft tissue masses. The study aim was to determine the incidence and diagnostic relevance of CSA in a consecutive series of superficial soft tissue masses referred to a specialist musculoskeletal sarcoma service. Methods: All patients referred over a 6 month period with a non-lipomatous superficial soft tissue mass were prospectively analysed. Patients characteristics (age, gender), lesion features (anatomical location, size, relationship to the skin and deep fascia), presence of CSA and final histopathological diagnosis were collected. The presence of CSA was statistically analysed against these clinical, imaging and histopathological variables. Results: 128 patients fulfilled the inclusion criteria [63 males, 65 females; mean age = 50.6 years (7-96 years)]. CSA was present in 50 cases (39.1%) overall, but in 39 (41.5%) of 94 cases with histological diagnosis. There was no statistically significant relationship to any assessed variable apart from relationship to the deep fascia, CSA being more frequent in lesions contacting the fascia compared to lesions contacting both skin and fascia (p-value 0.02). In particular, the presence of CSA did not allow differentiation between non-malignant and malignant lesions. Conclusion: The presence of CSA is a not infrequent finding in the MRI assessment of superficial soft tissue masses but does not appear to be of any significance in differentiating between non-malignant and malignant lesions. Advances in knowledge: CSA is a relatively common finding in association with superficial soft tissue masses, but does not indicate a particular histological diagnosis or help in the differentiation of non-malignant from malignant lesions.

Aneurysmal bone cyst (ABC) and telangiectatic osteosarcoma (TOS) share several clinical and imaging features, including young presentation, long bone involvement, lytic appearance on radiography and fluid-fluid levels on MRI. Therefore, they may be difficult to differentiate. The aim of this study is to identify clinical, radiological and MRI features which aid differentiation of the two lesions. Retrospective review of all histologically confirmed ABC and TOS over an 11-year period. Data recorded include age at presentation, sex, skeletal location and various radiographic and MRI features. This retrospective study included 183 patients, 92 males and 91 females. Mean age at presentation of 18.4 years (range 1–70 years); 152 cases of ABC and 31 TOS. No significant difference between age and sex. TOS was significantly less likely to involve the axial skeleton; no difference related to location within the bone. Radiographic findings significantly favouring ABC included a less aggressive pattern of bone destruction, a purely lytic appearance, an expanded but intact cortex, no periosteal response and no soft tissue mass. MRI features significantly favouring ABC included smaller tumour size (maximum mean dimension 46 mm compared to 95 mm for TOS), absence of soft tissue mass, > 2/3 of the lesion filled with fluid levels and thin septal enhancement following contrast. Several radiographic and MRI features aid in the differentiation between ABC and TOS. Lesions with a geographic Type 1A or IB pattern of bone destruction which are completely filled with FFLs on MRI can confidently be diagnosed as ABC.

To determine the incidence and diagnostic relevance of pathological fracture in patients with conventional central chondrosarcoma (CC-CS). Retrospective review of patients with CC-CS diagnosed between January 2007 and December 2019. Data collected included age, sex, skeletal location and the presence of pathological fracture at presentation. Histological tumour grade based on surgical resection or needle biopsy was classified as atypical cartilaginous tumour (ACT)/grade 1 CS (ACT/Gd1 CS), high-grade CS (HG-CS) and dedifferentiated CS (DD-CS). The presence of pathological fracture was correlated with age, skeletal location and tumour grade. Three hundred seventeen patients were included (177 males and 140 females with mean age 55.8 years, range 9–91 years). Mean age of patients without pathological fracture was 54.4 years and those with pathological fracture 62.9 years (p = 0.002). The major long bones were involved in 171 cases, the flat bones in 112 cases, the mobile spine in 7 cases and the small bones of the hands and feet in 27 cases. There were 81 ACT/Gd 1 CS, 168 HGCS and 68 DD-CS. Pathological fracture was evident at presentation in 51 (16.1%) cases, the commonest bones involved being the femur (n = 21; 41.2%), humerus (n = 10; 19.6%) and acetabulum (n = 7; 13.7%). Pathological facture occurred in 7 cases of ACT/Gd 1 CS (13.7%), 23 cases of HGCS (45.1%) and 21 cases of DD-CS (41.2%) (p = 0.001). Following multivariate analysis, both older age and histological grade were independently significant factors. Pathological fracture was seen in 16.1% of patients with CC-CS. Pathological fractures in the femur, humerus and acetabulum very likely indicate higher tumour grade.

Extra-articular posteromedial talocalcaneal coalition (EA-PM TCC) accounts for approximately one-third of TCC, but its radiographic features are not well-described. The current study aims to compare the radiographic features of EA-PM TCC with normal ankles and with the commoner forms of TCC. A retrospective review of cases of TCC over 12 years for whom radiographs, CT, and/or MRI study were available. Radiographs were assessed by 2 radiologists for the presence of the C-sign, talar beak, dysmorphic sustentaculum, absent middle facet, and prominence of the posterior subtalar joint. TCC was classified by a third radiologist based on CT/MRI findings into 3 groups: no TCC, EA-PM TCC, and other TCCs. The radiographic findings for the 3 groups were compared. The study included 50 patients, 28 males and 22 females with a mean age of 21.1 years (range 8–70 years). In 15 patients, both ankles had been imaged, resulting in a total of 65 cases. In 17 ankles, no TCC was identified, while 15 ankles were classified as EA-PM TCC and 33 as having other types of TCC. There were no statistically significant differentiating radiological features between the groups with no TCC and EA-PM TCC apart from prominence of the posterior subtalar joint, while only the C-sign allowed identification of patients with other types of TCC. The study suggests that EA-PM TCC cannot be diagnosed based on the classical indirect radiological signs of TCC, but can be identified by prominence of the posterior subtalar joint.

To evaluate the role of pre-biopsy MRI for management planning in patients with atypical cartilaginous tumours (ACT) diagnosed on image-guided core needle biopsy (IGCNB). Retrospective review of patients diagnosed with ACT of the appendicular skeleton based on IGCNB who subsequently underwent surgical curettage or resection. Data collected included age, sex, skeletal location and surgical histology classified as ACT, high-grade chondrosarcoma (HG-CS) and dedifferentiated chondrosarcoma (DD-CS). Pre-biopsy MRI studies were reviewed independently by 2 radiologists blinded to surgical histology results and graded as ACT, HG-CS and DD-CS based on MRI features. The study included 24 males and 28 females (mean age 42.1 years; range 9–76 years). One patient had 2 lesions treated, making a total of 53 lesions. Tumours were located in the femur in 21 cases, humerus in 17, tibia in 9, radius in 4 and ulna and fibula in 1 each. Surgical histology was ACT in 41 cases, HG-CS in 10 and DD-CS in 2, indicating mismatch between IGCNB and surgical histology in 12/53 cases (22.6%). Predicted MRI grade for the 2 readers was ACT in 39 cases each, HG-CS in 13 and 14 cases and DD-CS in 1 and 0 cases. Sensitivity, specificity and accuracy of MRI for predicting HG-CS/DD-CS were 91%, 93% and 92%, respectively. Inter-observer correlation was very good (kappa = 0.94). Review of MRI findings in patients with ACT diagnosed on IGCNB is vital for identifying patients with a HG-CS/DD-CS and is recommended when planning surgical management or considering repeat IGCNB.

To describe the MRI features of paediatric conventional central chondrosarcoma (CC-CS) and correlate with histological grade. A retrospective review of children/adolescents with histologically confirmed CC-CS. Data collected included age, sex, skeletal location, and histology from needle biopsy or resection, which was classified as atypical cartilaginous tumours/grade 1 CS (ACT/Gd 1 CS), high-grade chondrosarcoma (HGCS), and dedifferentiated chondrosarcoma (DD-CS). MRI studies were reviewed independently by 2 radiologists blinded to the histology grade, who graded the tumours as ACT/Gd 1 CS, HGCS, and DD-CS based on MRI features. The study included 7 males and 10 females with mean age 13.9 years (range 6–18 years). Tumours were located in the femur (n = 6), humerus (n = 3), tibia, ilium, scapula, and ulna (n = 1 each), and the small bones of the hands or feet (n = 4). Final histology grade was ACT/Gd 1 CS in 15 cases and HGCS in 2 (both grade 1 CS with focal transition to grade 2), 15 based on surgical specimens, 1 based on open biopsy, and 1 on needle biopsy alone. Predicted MRI grade for the 2 readers was ACT/Gd 1 CS in 11 cases each and HGCS in 6 cases each, indicating a mismatch between predicted MRI grade and histological grade in 8 (47%) cases (4 cases with one reader mismatch and 4 cases with both). MRI findings in paediatric CC-CS may be misleading, showing features suggestive of HGCS 7 of 17 (41.2%) of cases. This should be taken into consideration when planning surgical treatment.

Aims This pilot study aims to determine if tumour heterogeneity assessed using magnetic resonance imaging (MRI) radiomics-based texture analysis (TA) can differentiate between lipoma and atypical lipomatous tumour (ALT)/well-differentiated liposarcoma (WDL). Materials and methods Thirty consecutive ALT/WDLs and 30 lipomas were included in the study, cases diagnosed both histologically and with murine double minute 2 (MDM2) gene amplification by fluorescence in situ hybridisation (FISH) in excision specimens. Multiple patient, MRI and MRTA factors were assessed. Heterogeneity was evaluated using a filtration-histogram technique-based textural analysis on single axial proton density (PD) and coronal T1-W images of the most homogenously fatty component of the lesion. Results Thirty-three percent of the diagnoses of ALT/WDL vs lipoma were confirmed using FISH MDM2 analysis. ALT/WDLs were statistically different from lipomas in location (site in the body and depth from skin surface) and fat content, with p values of 0.021, 0.001, and 0.021 respectively. Nine of 36 (25%) texture parameters had significant differences between ALT/WDLs and lipomas on axial PD MRTA, with the most significant results at medium and coarse texture scales particularly mean intensity (p = 0.003) at SSF = 6, and kurtosis (p = 0.012) at SSF = 5. A cut-off value of < 304 for coarse-filtered texture on axial PD MRI identified ALT from lipoma with a sensitivity and specificity of 70% (AUC = 0.73, p = 0.003). Conclusions Texture heterogeneity quantified at fine, medium, and coarse texture scales are significant differentiators of lipoma and ALT/WDL with the difference particularly marked in medium and coarse texture scales for two MR TA parameters: mean and kurtosis.