liposclerosing myxofibrous tumour (LSMFT)

Bone SPECT/CT

imaging of a liposclerosing myxofibroid tumor in an unexpected localization. CT images in transversal (a) and coronal plane (b) showed the “landscape-like” structure of the lesion in the left iliac bone with components of fat density (arrows). MRI revealed a hypointense center (short arrows) of the lesion in both T2 (c) and T1-weighted (d) coronal MRI images with rim enhancement (long arrows) after application of contrast media (d)

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Bone SPECT/CT

imaging of a liposclerosing myxofibroid tumor in an unexpected localization. Planar bone scan (a, dorsal view) showed no hyperperfusion (not shown) but increased blood pool in the left iliac bone in the early images 5 min p.i. (above) and a moderately enhanced tracer uptake in the delayed phase images (bottom). In SPECT/CT images 2 h p.i. (transversal view in b, coronal view in c), the lesion is easily visible with an inhomogeneous tracer uptake, slightly accentuated in the peripheral zone. Histology (HE staining) revealed lamellar and woven bone with curvilinear and pseudopagetoid features, accompanied by a moderately cellular intertrabecular fibrous stroma (d, magnification 100x). In some areas, clusters of foamy histiocytes were present (e, magnification 200x)

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Radiopaedia • CC-by-nc-sa 3.0 • de

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