Lipomas are the most commonly encountered soft tissue lesions on general ultrasound lists.The main differential for a lipoma is a low-grade liposarcoma, which can be challenging to distinguish on ultrasound. Currently there is no national guidance on when to request further imaging for suspiciouslipomas. The American College of Radiology (ACR) suggest that ultrasound is ‘usually appropriate’ for clinically suspected ‘internally simple and well-encapsulated lesions’, howeverMRI is required for lipomas demonstrating suspicious features. These features include heterogeneity, large size (>5cm), vascularity, ill-defined margins and intramuscular location....

We performed a search of our imaging database using the keyword ‘lipoma’, to identifiy relevant soft tissue ultrasounds performed over a six month period. The first 150 reports were included in our study as a 'random' representation of our regular practise. We then examined all reports for two main criteria: 1) A complete report commenting on the relevant positive and negative findings: Heterogeneity Size (< 5 cm/ >5cm) Vascularity Borders (well-defined/ill-defined) Depth (subcutaneous/ deep intramuscular) 2) Evidence of escalation to MRI when suspicious features aredemonstrated...

Of the 150 ultrasound studies querying lipoma, 125 identified a mass and 109 of these were defined as lipomas (N=109). ATYPIA Deep >5cm Ill-defined Heterogenous Hypervascular n 5 (4.6%) 16 (6.8%) 7 (6.5%) 9 (8.3%) 1 (1%) Not reported 34 4 13 28 27 Atypical Cases N = 38 MRI advised 6 MRI performed within 6 months 4 The results demonstrate that of our sampled lipoma reports (n=109), only 88 (81%) commented on all five criteria. The most commonly omitted descriptors were depth, heterogeneity and...

Our study indicates that as Radiologists/Sonographers we may be under-investigating complex lipomas.Based on our findings, we introducea lipoma imaging pathway to help streamline decision-making at our local department ( Fig. 4 ). After implementation, we plan to review our imaging practise, to see whether we can increase the specificity of our pathwayto further optimise our MRI referrals.

1. American College of Radiologists ACR Appropriateness Criteria. https://acsearch.acr.org/docs/69434/Narrative/

Nishanth Sivarasan, Radiology Registrar, Guy's and St Thomas' Hospital, London Christopher Tang, Radiology Registrar, Guy's and St Thomas' Hospital, London Ali Zavareh, Consultant Muskuloskeletal Radiologist, Guy's and St Thomas' Hospital, London