In-phase and opposed-phase Dixon chemical shift imaging for the assessment of skeletal marrow lesions: comparison of measurements from longitudinal sequences to those from axial sequences.

OBJECTIVE: In-phase and opposed-phase chemical shift imaging (CSI) is a useful technique for assessing skeletal lesions. This study determined the frequency of significant differences in measurements obtained from longitudinal (coronal or sagittal) sequences to those obtained from axial sequences. METHODS: Chemical shift imaging was undertaken in 96 consecutive patients referred from the Musculoskeletal Sarcoma and Spinal Oncology services for assessment of possible bone tumours as part of a standard tumour protocol, which included turbo spin echo and inversion recovery sequences. For spinal lesions, CSI was obtained in the sagittal and axial planes, while for all other sites, it was obtained in the coronal and axial planes. RESULTS: The study included 49 (51.0%) males and 47 (49.0%) females with mean age 42.4 years (range 2-91 years). In 4 cases, 2 individual lesions were assessed, making a total of 100 lesions. Based on typical imaging features (n = 57) or histology (n = 43), 22 lesions (22%) were classified as non-neoplastic, 44 (44%) as benign neoplasms, 6 (6%) as intermediate-grade neoplasms, and 28 (28%) as malignant neoplasms. A significant discrepancy, wherein a lesion was classified as fat-containing (% SI drop >20%-25%) in the longitudinal plane, while in the axial plane it was classified as fat-replacing (% SI drop <20%-25%), or vice versa, occurred in 9%-14% of cases. However, this discrepancy had no appreciable effect on overall diagnostic accuracy, which was calculated at 79% for the longitudinal plane and 75%-80% for the axial plane. CONCLUSIONS: Significant differences in CSI measurements occur in 9%-14% of cases based on imaging plane, but with no significant effect on diagnostic accuracy. ADVANCES IN KNOWLEDGE: Radiologists should be aware that CSI measurements in different planes appear to have significant differences in up to 14% of lesions. However, diagnostic accuracy does not seem to be significantly affected.

Image-guided synovial biopsy with a focus on infection.

Image-guided biopsy of the synovium is a relatively uncommon but safe procedure with a high-diagnostic yield in the correct clinical scenario. Whilst surgical and arthroscopic techniques are still commonly performed and remain the gold standard, they are more invasive, expensive and not widely available. Ultrasound and X-ray-guided synovial biopsy are being increasingly performed by radiologists to diagnose both native and periprosthetic joint infection (PJI) to guide surgical and microbiological management. The purpose of this review article is to present the historical background to synovial biopsy particularly related to potential joint infection, including common and uncommon pathogens encountered, sampling techniques and pitfalls, focusing mainly on its role in PJI and its role in patient pathways and decision-making within a joint infection multi-disciplinary framework.

Skip metastases in appendicular Ewing sarcoma: relationship to distant metastases at diagnosis, chemotherapy response and overall survival.

OBJECTIVE: To identify in appendicular Ewing sarcoma (ES), if skip metastases (SM) are associated with distant metastases at presentation, response to neoadjuvant chemotherapy and overall outcome. MATERIALS AND METHOD: Patients with appendicular ES from 2007 to 2021 who had whole-bone MRI to identify SM were included in the study. Patient demographics included age/gender, bone involved, the presence of SM, longitudinal tumour length, presence of extra-osseous disease and its axial depth if present from whole-bone MRI and lung metastases and distant bone metastases from staging studies. Response to neoadjuvant chemotherapy from resection specimens and overall survival were noted. Comparison of these factors between patients with and without SM was undertaken. RESULTS: Ninety-five patients (66 males; 29 females: mean age 15.8 years; range 5-48 years) were included. On whole-bone MRI, 80 (84.2%) patients had no SM and 15 (15.8%) patients had one or more SM. Of patients without a SM, lung metastases were present in 16 (21%), distant bone metastases in 7 (11%), while 51 (75%) had a good response to chemotherapy compared with 7 (50%), 3 (27%), and 10 (77%), respectively, in patients with a SM. SM were significantly associated with lung metastases (p = 0.02), but not with distant skeletal metastases (p = 0.13), chemotherapy response (p = 0.88), tumour length (p = 0.47), presence of (p = 0.15) or axial depth of extra-osseous disease (p = 0.4). SM were associated with a significantly poorer survival (p = 0.007) and three times greater risk of death during follow-up. CONCLUSIONS: In appendicular ES, the identification of a SM is associated with the presence of lung metastases at presentation and poorer survival.

Skip metastases in high-grade intramedullary appendicular osteosarcoma: an indicator of more aggressive disease?

OBJECTIVE: To determine whether skip metastases (SM) in high-grade appendicular osteosarcoma (HG-OS) are an indicator of more aggressive disease. MATERIALS AND METHOD: Retrospective review of patients with histologically confirmed diagnosis HG-OS of the long bones from 2007 to 2020, who had whole-bone MRI to identify SM. Data collected included patient age/gender, bone involved, the presence of SM, the presence of lung metastases from chest CT, the presence of distant bone metastases from whole-body bone scintigraphy or whole-body MRI, and chemotherapy response from resection specimen histology. The presence of lung or bone metastases and chemotherapy response were compared between patients without and with SM. RESULTS: The study included 241 patients (146 males; 95 females: mean age 18.2 years; range 4-73 years). Based on whole-bone MRI, 202 (83.8%) patients had no SM and 39 (16.2%) patients had a SM. Of patients without a SM, lung metastases were identified in 44 (22%) and distant bone metastases in 6 (3%) cases, while 80 (43%) had a good chemotherapy response and 105 (57%) had a poor chemotherapy response. Of patients with a SM, lung metastases were identified in 22 (58%) and distant bone metastases in 8 (21%) cases, while 11 (32%) had a good chemotherapy response and 23 (68%) had a poor chemotherapy response. The presence of SM was significantly associated with both lung metastases (p < 0.001) and skeletal metastases (p < 0.001), but not with chemotherapy response (p = 0.24). Patients with SM also had poorer survival (p < 0.001). CONCLUSIONS: The presence of SM in appendicular HG-OS suggests more aggressive disease.

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.

Comparison of lumbar degenerative disc disease using conventional fast spin echo T2W MRI and T2 fast spin echo dixon sequences.

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 T1weighted turbo spin echo (T1W TSE), T2weighted fast spin echo (T2W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T2W 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 T2W 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 T2W 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 T1W TSE, T2W FSE and STIR sequences with a T2W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.

Paediatric bone lesions: diagnostic accuracy of imaging correlation and CT-guided needle biopsy for differentiating benign from malignant lesions.

OBJECTIVE: To determine the sensitivity, specificity and accuracy of CT-guided needle biopsy (CT-NB) for distinguishing benign and malignant lesions in children with suspected primary bone tumours, and to assess the correlation between imaging diagnosis and final diagnosis. METHODS: Retrospective review of children who underwent CT-NB of a suspected primary bone tumour between October 2016 and October 2019. Data collected included anatomical location, imaging diagnosis, type of needle, type of biopsy sample, CT-NB diagnosis, final diagnosis and post-procedural complications. The final diagnosis was established based on surgical histology or clinical/imaging follow-up. RESULTS: 125 patients met the inclusion criteria (68M, 57F: mean age 11 years; range 10 months-18 years). Biopsy was performed using a 10 cm Jamshidi needle (10G n = 96; 13 G n = 8); 14G Tru-Cut needle (n = 18); 14G Temno needle (n = 3). The commonest anatomical locations were the femur (n = 40), tibia (n = 25) and humerus (n = 16), while the commonest diagnoses were osteosarcoma (n = 35), CRMO (n = 15) and LCH (n = 14). A benign tumour was correctly identified on imaging in 100% of cases, and a malignant tumour in 95.8%. Sensitivity, specificity and diagnostic accuracy of CT-NB for distinguishing malignant from benign lesions were 98%, 100 and 99%. Of 24 indeterminate biopsy results, all that had a non-aggressive radiological appearance were benign. No immediate complications were recorded. CONCLUSION: CT-NB represents a safe and very effective tool for differentiating benign and malignant lesions in children presenting with a suspected primary bone tumour. Suspected radiological diagnosis plays a pivotal role in the management of indeterminate biopsy results. ADVANCES IN KNOWLEDGE: Paediatric bone tumours pose a significant diagnostic and therapeutic challenge. The interpretation of the imaging findings is essential for the successful management of indeterminate histological results.

Role of in-phase and out-of-phase chemical shift MRI in differentiation of non-neoplastic versus neoplastic benign and malignant marrow lesions.

OBJECTIVE: To determine its ability of in-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) to distinguish non-neoplastic marrow lesions, benign bone tumours and malignant bone tumours. METHODS: CSI was introduced into our musculoskeletal tumour protocol in May 2018 to aid in characterisation of suspected bone tumours. The % signal intensity (SI) drop between IP and OOP sequences was calculated and compared to the final lesion diagnosis, which was classified as non-neoplastic (NN), benign neoplastic (BN) or malignant neoplastic (MN). RESULTS: The study included 174 patients (84 males; 90 females: mean age 44.2 years, range 2-87 years). Based on either imaging features (n = 105) or histology (n = 69), 44 lesions (25.3%) were classified as NN, 66 (37.9%) as BN and 64 (36.8%) as MN. Mean % SI drop on OOP for NN lesions was 36.6%, for BN 3.19% and for MN 3.24% (p < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of CSI for differentiating NN from neoplastic lesions were 65.9%, 94.6%, 80.6%, 89.1%% and 87.4% respectively, and for differentiating BN from MN were 9.1%, 98.4%, 85.7%, 51.2 and 53.1% respectively. CONCLUSION: CSI is accurate for differentiating non-neoplastic and neoplastic marrow lesions, but is of no value in differentiating malignant bone tumours from non-fat containing benign bone tumours. ADVANCES IN KNOWLEDGE: CSI is of value for differentiating non-neoplastic marrow lesions from neoplastic lesions, but not for differentiating benign bone tumours from malignant bone tumours as has been previously reported.

Comparison of in-phase and opposed-phase T1W gradient echo and T2W fast spin echo dixon chemical shift imaging for the assessment of non-neoplastic, benign neoplastic and malignant marrow lesions.

OBJECTIVE: The objective of this study is to compare T1-weighted gradient echo (T1W GrE: control technique) chemical shift imaging (CSI) with T2-weighted fast spin echo (T2W FSE: experimental technique) CSI for differentiating non-neoplastic and neoplastic marrow lesions. MATERIALS AND METHODS: Patients undergoing MRI for various marrow lesions were investigated with T1W GrE and T2W FSE Dixon CSI. Signal intensity (SI) change between in-phase (IP) and opposed-phase (OP) sequences was calculated, and SI drop > 20% considered to represent non-neoplastic lesions while SI drop < 20% considered to represent neoplastic lesions. Final diagnosis was based on imaging features (n = 42) or histology (n = 43) and classified as non-neoplastic, benign neoplastic, and malignant neoplastic. Inter-observer and inter-technique agreement between 2 readers was calculated. RESULTS: The study included 85 patients (44 males and 41 females; mean age 41.1 years, range 2-83 years). Final diagnosis included 19 (22.4%) non-neoplastic lesions, 27 (31.8%) benign neoplasms, and 39 (45.9%) malignant neoplasms. On T1W GrE CSI, 19-21 lesions were classed as non-neoplastic and 64-66 as neoplastic, while on T2W FSE Dixon CSI, 22-24 lesions were classed as non-neoplastic and 61-64 as neoplastic. Lesion classification matched between the 2 techniques in 91.8-96.5% of cases. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of T1W GrE CSI for differentiating non-neoplastic and neoplastic marrow lesions were 66.7-72.2%, 88.1-89.6%, 61.9-63.2%, 90.9-92.2%, and 84.7%, and of T2W FSE Dixon CSI were 72.2-77.8%, 85.1-86.6%, 58.3-59.1%, 92.1-93.4%, and 83.5%. CONCLUSIONS: T1W GrE CSI and T2W FSE Dixon CSI produce similar results in the assessment of non-neoplastic and neoplastic marrow lesions.

Accessory flexor carpi ulnaris: case report and review of the literature.

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.

Description of the MRI and ultrasound imaging features of giant epidermal cysts.

OBJECTIVES: Guidelines suggest that lesions over 5 cm in dimension should be referred to a specialist sarcoma centre due to the possibility of malignancy. Few epidermal cysts (ECs) reach or exceed this size and are termed giant ECs (GECs). The purpose of this study is to report on a large series of GECs. METHODS: Retrospective review of histologically proven GECs over an 8-year period. Patient demographics with MRI and ultrasound (US) appearances were evaluated. RESULTS: A total of 14 cases were included with eight males and six females. Mean age was 51 years. 11 lesions were oval and three bi-lobed in shape, while 12 demonstrated dermal apposition. All were hyperintense on water-sensitive sequences and isointense to slightly hypointense on T1W imaging. Internal clefts were seen in 13 cases and 11 demonstrated chemical shift artefact (CSA) on MRI. On US, 12 showed well-defined linear hypoechoic clefts, with 66.6% having dis-organised compared with 33.3% peripherally located clefts. One 'pseudo testis' pattern and one showing irregular striped echogenicity termed novel 'pseudo muscle' appearance. No cases demonstrated internal vascularity on Doppler US. CONCLUSIONS: MRI signal findings of GECs are often characteristic with hyperintensity on water-sensitive sequences, dermal apposition, CSA and internal clefts while US features of disorganised or clumped hypoechoic clefts and absence of neovascularity were commonly seen. Recognition of combinations of both US and MRI features of GECs should reduce the requirement for pre-excisional needle biopsy to confirm the diagnosis. ADVANCES IN KNOWLEDGE: 1. Identification of common imaging features of GECs should avoid unnecessary pre-excisional biopsy despite their large size in the appropriate MDT setting.2. A novel 'pseudo-muscle' appearance is described on MRI and US.

Pilot study to differentiate lipoma from atypical lipomatous tumour/well-differentiated liposarcoma using MR radiomics-based texture analysis.

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.

The radiological diagnosis of extra-articular posteromedial talocalcaneal coalition.

OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

The differentiation between aneurysmal bone cyst and telangiectatic osteosarcoma: a clinical, radiographic and MRI study.

OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Anomalous signal intensity increase on out-of-phase chemical shift imaging: a manifestation of marrow mineralisation?

OBJECTIVE: In-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) is an established technique for clarifying the nature of indeterminate bone marrow lesions, a signal intensity (SI) drop of > 20% at 1.5 tesla (T) or > 25% on 3 T on the OOP sequence being consistent with a non-neoplastic process. Occasionally, SI increase is seen on OOP sequences. The aim of this study is to determine if this is related to marrow sclerosis or matrix mineralisation. MATERIALS AND METHODS: In 184 cases, the SI change on OOP was calculated. For patients in whom the SI on OOP increased compared with the IP sequence, available CT studies and radiographs were reviewed to look for marrow sclerosis and/or matrix mineralisation. RESULTS: Forty out of 184 patients (34.25%) showed an anomalous increase in SI on the OOP sequence. CT studies were available in 27 cases (67.5%), of which medullary sclerosis was seen in 20 (74.1%) while matrix mineralisation was seen in a further 2 cases. Review of radiographs demonstrated matrix mineralisation in 6 cases, while punctate signal void consistent with chondral calcification was seen on MRI in 2 more cases. Based on either typical imaging features (n = 22) or histology (n = 18), 7 lesions (17.5%) were classed as non-neoplastic, 18 (45%) as benign neoplasms and 15 (37.5%) as malignant neoplasms. CONCLUSION: When assessing focal marrow lesions with CSI, anomalous SI increase may be seen on the OOP sequence in approximately one-third of cases. In over 75% of such cases, CT or radiographs demonstrate either diffuse marrow sclerosis or matrix mineralisation.

Small indeterminate superficial soft tissue masses: relationship between depth and histological grade.

OBJECTIVE: To determine whether the location of a small, indeterminate soft tissue mass within the subcutaneous compartment is related to its histological grade. METHODS: All Sarcoma Service referrals over a 12 month period of small (<3 cm) superficial soft tissue masses, indeterminate by MRI evaluation which subsequently underwent primary excision biopsy were included. Lesions were categorised by their anatomical location in the subcutaneous compartment. Histopathological diagnoses were categorized according to12 WHO 2013. χ2 statistical analysis was performed to determine the relationship between lesion depth and histological grade. RESULTS: The study included 43 patients, mean age 42 years (range 15-71 years). Within the subcutaneous compartment, 16 lesions were categorized as superficial, 9 lesions central and 18 lesions deep, of which 9 were non-neoplastic, 29 benign, 1 intermediate-grade and 4 malignant. Location in the deep aspect of the subcutaneous compartment was associated with a higher risk of intermediate or malignant histology (p = 0.02). CONCLUSION: The location of a small, indeterminate soft tissue mass within the subcutaneous compartment may be an indicator of histological aggressiveness. Lesions in the deep subcutaneous compartment are more likely to be intermediate-grade/malignant lesions. Therefore, if considering excision biopsy as definitive treatment, a wider margin may be appropriate. ADVANCES IN KNOWLEDGE: Small, indeterminate soft tissue masses can be aggressive and the anatomical depth within the subcutaneous tissue may be a potential indicator of histological aggressiveness.