liposclerosing myxofibrous tumor

Liposclerosing myxofibrous tumors (LSMFT), also known as polymorphic fibro-osseous lesions of bone, are rare benign fibro-osseous lesions that have a predilection for the intertrochanteric region of the femur.

Clinical presentation

It is slightly more common in males with mean age of 30-40 years. It can be discovered incidentally but mostly patients have vague longstanding pain. About 10% of patients present acutely with pathologic fracture.

Pathology

The tumor comprises of the wide mixture of tissues of lipomatous, fibroxanthomatous, myxomatous, and myxofibromatous components inclusive.

Location

Tends to have a striking predilection for the intertrochanteric region of the femur (80-90%) .

Radiographic features

Plain radiograph/CT 
  • geographic lucent lesion usually centered in intertrochanteric region of the proximal femur
  • sclerotic margin
  • mildly expansile
  • multilocular
  • matrix calcification in ~70% of cases
  • fat density component
MRI

Despite its name, distinct fatty components are not seen

  • T1: relatively homogeneous and isointense to skeletal muscle
  • T2: moderately heterogeneous with areas of high signal due to myxoid component
Nuclear medicine

Scintigraphy can show mild focal uptake with Tc-99m pertechnetate .

Treatment and prognosis

  • incidentally detected asymptomatic lesions: no treatment or intervention
  • symptomatic lesions: are commonly managed with bone curettage, bone grafting, and fixation
  • pathological fracture: uncommon ~10%; proximal femoral lesions may require arthroplasty
  • malignant transformation: rare but documented 10-15%; transformation into osteosarcoma is the most common

Due to this potential malignant transformation, lesions need follow-up imaging preferably by MRI. Symptomatic lesions or those with interval change require surgical resection .

Differential diagnosis

On radiographs consider:

  • fibrous dysplasia: it is challenging to differentiate between both by imaging. Fibrous dysplasia may show less sclerosis by radiography, more uptake by scintigraphy and intermediate or low signal intensity by fluid sensitive MRI sequences
  • intraosseous lipoma: LSMFT does not usually show macroscopic fat on CT or MRI as lipomatous component is usually too small and mixed with other more prominent myxofibrous or fibro-osseous tissue
  • aneurysmal bone cyst (ABC): usually more expansile 
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