Liposclerosing myxofibrous tumor
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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.
The histopathological origin of this lesion is unclear and under discussion 1-3.
According to the WHO classification of soft tissue and bone tumors (5th edition) the term "liposclerosing myxofibrous tumor" is no longer recommended and instead, fibrous dysplasia is preferred.
Liposclerosing myxofibrous tumors can occur in a wide age range with a peak in the 4th decade of life 2-4. Men and women seem to be equally affected 2.
It can be discovered incidentally but most patients have vague longstanding pain. About 10% of patients present acutely with pathologic fracture ref.
The tumor comprises a wide mixture of tissues of histological elements including lipomatous, fibroxanthomatous, myxomatous, and myxofibromatous components 5 and is not a universally accepted pathological entity 3.
Tends to have a striking predilection for the intertrochanteric region of the femur (80-90%) 6-8. Beyond that, it might occur in the humerus the tibia, ilium and ribs 5.
Histologically liposclerosing myxofibrous tumors are characterized by the following 2,5:
- bland myxoid and fibrous background
- adipose tissue
- foamy macrophages
- curved bony trabeculae of woven bone
- cementum-like ossicles
Generally, it displays similarities to the histological appearance of fibrous dysplasia and beyond that ischemic and lipomatous changes 3.
On plain radiographs and CT liposclerosing myxofibrous tumors are characterized by the following 4,5:
- geographic lucent lesion usually centered in the intertrochanteric region
- sclerotic margin
- mildly expansile
- matrix calcification in ~70% of cases
- fat density component
Despite its name, distinct fatty components are not seen on MRI as the lipomatous component is usually too small and mixed with other more prominent myxofibrous or fibro-osseous tissue.
- T1: relatively homogeneous and isointense to skeletal muscle
- T2: moderately heterogeneous with areas of high signal due to myxoid component
Scintigraphy can show mild focal uptake with Tc-99m pertechnetate 6.
Treatment and prognosis
- incidentally detected asymptomatic lesions: no treatment or intervention 6
- symptomatic lesions: are commonly managed with bone curettage, bone grafting, and fixation 6
- pathological fracture: uncommon ~10%; proximal femoral lesions may require arthroplasty 6
- 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 8.
History and etymology
The term "liposclerosing myxofibrous tumor" has been first proposed and introduced in 1986 by the American pathologists, Bruce D. Ragsdale and Donald E. Sweet 3,9.
- 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 6
- non-ossifying fibroma
- intraosseous lipoma: in contrast to liposclerosing myxofibrous tumors intraosseous lipoma is characterized by evidence of macroscopic fat on CT or MRI
- aneurysmal bone cyst (ABC): usually more expansile
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