LIPOMA COMMONEST SOFT TISSUE TUMOUR

Aim: To assess ultrasound characteristics of a lipoma that may suggest atypical nature or frank sarcoma Study: Population; 53 lipomas, 50 sarcomas. All biopsy proven after ultrasound and other cross sectional imaging.

Method; 103 consecutive referrals to the sarcoma service or radiology for imaging of soft tissue lumps. Assessed initially by ultrasound with correlative MRI and biopsy with end product of histology from the surgical specimen. Results; Benign lipomas- 53. (US suggested 51 lipomas, 2 atypical- HISTOLOGY ALL LIPOMAS. ) Sarcomas – 50 (US suggested sarcoma in all)

50 LIPOMAS, 3 ATYPICAL YEARS FEATURESLIPOMAATYPICAL >5CM120 <5CM383 SUPERFICIAL402 DEEP101 DOPPLER30 HYPERECHOIC7*0 ISO/HYPOECHOIC333 * ANGIOLIPOMA

ELASTOGRAPHY FEATURESLIPOMAATYPICAL GREEN, BLUE481 BLACK22 STRAIN RATIO (AVE=1.2) (AVE=1.23) (AVE 1.17)

103 patients-53lipomas, 50 sarcomas Featureslipomasarcoma >5cm diameter1221 Deep1030 Dopp pos328 Irreg contour122 Complex internal130 Volume D ave= ave=134.8 Volume S1-100 ave= Ave 26.9

Conclusion; Important features for ultrasound diagnosis lipoma- hypo/hyperechoic with thin stromal lines parallel to skin. Hyperchoic types are due to angiolipomas Doppler, regularity of wall, size/volume has little correlation with sarcomatous change/ atypia when the above characteristic features are present. DEEP lesions may be harder for ultrasound to characterise- proceed to MR Key features to differentiate sarcomas in absence of typical lipoma stromal morphology are; complexity of ultrasound signal, irregular margins, Doppler. 40% sarcomas superficial, 60% deep.

Ideas from BSSR… in our diagnostic MDT, we only discuss lipomas if there is a concern. For example: if the reporting radiologist or the surgeon has a clinical concern such as lesion heterogeneity, significant progression etc: we donot use any size criteria for determing whether a lipoma is discussed or not. >7cm subcut, any size deep to fascia, symptomatic/growing come to MDT. We are working under the Leeds Sarcoma MDT rules - they take any small lipomata with worrying features and otherwise lipomata >7cm; our local plastic surgeons take lumps between 5-7cm with a view to excision biopsy and anything less than that is referred back to the GP for surveillance.

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