Radiology Resident Case of the Week: August 11, 1995

Disease: Intraosseous lipoma = Bone lipoma

Eric Fitzcharles, M.D.
Peer Review Status: Internally Peer Reviewed

Clinical Sx:
70% get minor aching for days to years. 20% get swelling with or without pain. 25% are asymptomatic upon discovery. Compression of neighboring structures (ie. nerve) is possible but not common.

Etiology/Pathophysiology:
1.4/1 male/female ratio; any age >10 yrs; may be associated with hyperlipoproteinemia.

Pathology:
fat: both necrotic and live cells, with trabecular thinning and dysmorphic calcifications

Miscellaneous:
No reported cases of malignant transformation. Fracture is a possible complication; if there is structural concern, curettage and packing is the treatment of choice, and lipoma will not recur.

Imaging:
Location: epiphysis or metaphysis >> shaft; calcaneus, extremities (proximal femur > tibia, fibula, humerus), skull, ribs. Lytic, expansile, radiolucent lesion often with sclerotic rind and cortical thinning overlying; may see loculated, septated appearance secondary to residual trabeculae; often see calcified clumps centrally secondary to fat necrosis. MR shows fat intensity.

DDx:

1. infarct - but these are not expansile

2. enchondroma - not usually expansile

3. chondrosarcoma - not usually as well circumscribed

4. fibrous dysplasia - usually hot on bone scan, lipoma usually cool unless fracture is present

Key References:
1. Dahnert, Wolfgang, Radiology Review Manual, 2nd ed.
2. Mirra, Joseph, Bone Tumors, 1989.

ACR Code:
4.319

Keywords:
Intraosseous lipoma, bone lipoma

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