Rare in children

Painless, slow growth when subcutaneous

Intramuscular lipomas can cause mild activity-related pain

Superficial lipomas are more common in the shoulders, back, neck, and abdomen

Intramuscular lipomas are more common in the lower extremities

Uniform high signal on T1 and suppression on fat-suppressed images

MRI is diagnostic for lipoma when the lesion is identical to subcutaneous fat on all pulse sequences

Lipomas are radiolucent relative to muscle on radiographs ( left ) and CT ( righ t). Note the small, thin single septum anteriorly on CT.

Intramuscular lipomas often attain large size before diagnosis.

The signal intensity of the lipoma should be the same as that of subcutaneous fat on all pulse sequences, as can be seen on these T1 ( left ) and fat-suppressed T2 ( right ) MRI images.

Subcutaneous lipomas can appear well encapsulated ( arrows ) and distinct from the surrounding subcutaneous tissue ( left ).

They can also appear to blend into the surrounding tissue ( arrow, right ). On physical examination, superficial lipomas have a soft, doughy consistency.

Lipomas can appear more complex in approximately 30% of cases, as observed in these periscapular ( left ) and thigh ( right ) lipomas.

While this may suggest a diagnosis of well-differentiated liposarcoma, as seen here, the septations in a lipoma should be less than 2 to 3 mm and not thicker than the nearby subcutaneous fat ( stars ).