Lipoma: Benign soft tissue tumor composed of mature adipose tissue

Subcutaneous location more common than subfascial (intra- or intermuscular)

Well-defined, oblong-shaped, encapsulated mass

Fine linear striations parallel to long axis of tumor

Hyper- or isoechoic to adjacent fat with absent or minimal color Doppler flow

Compressible similar to adjacent fat

Most common soft tissue tumor

Soft, well-defined, painless mass enlarging over months, often during period of weight gain

Classic appearance can be diagnosed definitively with ultrasound

Atypical appearance needs evaluation with MR or biopsy

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  Large size, deep location, heterogeneity, vascularity, crossing fascial planes, rapid growth

MR is better than ultrasound in differentiation of benign or malignant lipoma and in assessing deep masses

Scan in area directed by patient in position they report is most exacerbating

Use compression to demonstrate soft character of mass

Use extended field of view to capture larger masses

Use light pressure when assessing for color Doppler flow to avoid false absence from compression

Look for “neck” as fat-containing ventral and lumbar hernias can mimic lipomas