J McNamee, G Briggs, D Gracey.
Musgrave Park Hospital,
Stockman’s Lane, Belfast,
Norther Ireland BT9 7JB
Section: Musculoskeletal System
Published: 2012, Jul. 17
Patient: 53 year(s), female
Clinical History
Persistent left proximal hip pain for three months. Tender on examination. No history of trauma.
Imaging Findings
X-ray of the pelvis shows a well-defined lucency within the metaphysis of the proximal femur. It has a thin, sclerotic margin and contains internal ossification. There is no periosteal reaction or pathological fracture.
MRI confirms a 1.7 cm, intramedullary lesion which is isointense to muscle on T1 and high on T2 with central low-signal calcific foci. A small amount of T1-high signal is seen at the superior aspect of the lesion, in keeping with fat. There is no evidence of cortical destruction and no soft tissue component is seen.
Discussion
Liposclerosing myxofibrous tumour of bone (LSMFT) is a fibro-osseous lesion that is characterised by a complex mixture of histological elements. The location in the intertrochanteric region of the femur is the key element to consideration of this diagnosis [1].
Histologically, it is characterised by a mixture of elements, including lipoma, fibroxanthoma, myxoma, myxofibroma, fibrous dysplasia-like features, cyst formation, fat necrosis, ischaemic ossification and rarely cartilage [2].
The origin of LSMFT is unclear. The most common theories suggest it is a variant of fibrous dysplasia or it represents degenerative change in benign entities such as lipomas, simple bone cysts, fibromyxomas or bone infarcts [1, 2, 3].
LSMFT most commonly presents with pain but has been discovered as an incidental finding [1]. It can also present as a pathological fracture. It usually occurs in the fourth to sixth decades with an equal distribution between men and women. Whilst it is generally considered benign, there is a well documented risk of malignant transformation of between 10-16% [1, 2, 3, 4]. Transformation into osteosarcoma, fibrosarcoma and malignant fibrous histiocytoma has been demonstrated [1].
Malignant transformation has been linked to lesions containing necrotic fat with secondary calcification and reactive ossification with ischaemic woven bone [4]. It has been suggested that malignant transformation may occur within the reactive border of ischaemic bone or arise from atypical
lipomatous elements [1, 4, 5].
The role of the radiologist is to make the initial diagnosis and exclude other differentials. It is most specifically characterised by its location with over 90% of lesions occurring in the central metadiaphysis of the proximal femur. The imaging features are non-aggressive, with the classic description being that of a lucent lesion with a narrow zone of transition, thin sclerotic border and internal mineralised matrix. On MRI, it is isointense to muscle on T1 and predominantly high signal on T2, with areas of low signal corresponding to the mineralised matrix.
The significant risk of malignant transformation in LSMFT necessitates the need for close observation. Biopsy should be performed on patients who are symptomatic or who have deteriorating symptomatology. Asymptomatic patients are followed up with serial MRI.
In summary, liposclerosing myxofibrous tumour of bone is a complex histological lesion with characteristic radiological findings and a strong predilection for the intertrochanteric region of the femur. The significant risk of malignant transformation necessitates the need for close observation of this lesion [1].
Differential Diagnosis List
Fibrous Dysplasia, Intraosseous Lipoma, Simple Bone Cyst, Bone Infarct
Figures
Figure 1. X-ray Left Hip
X-ray of the pelvis shows a well-defined lucency within the metaphysis of the proximal femur. It has a thin, sclerotic margin and contains internal ossification. There is no periosteal reaction or pathological fracture.
Figure 2. Coronal T1W MRI Left Hip
MRI confirms a 1.7 cm, intramedullary lesion which is isointense to muscle on T1 with a thin sclerotic rim. Some high signal foci are seen superiorly in keeping with fat.
Figure 3. Axial T2W MRI Left Hip
The lesion is high signal on T2 with low signal calcific foci within it.
References
[1] Mark J. Kransdorf, MD, Mark D. Murphey, MD and Donald E. Sweet, MD (1999) Liposclerosing Myxofibrous Tumor: A Radiologic-Pathologic-Distinct Fibroosseous Lesion of Bone with a Marked Predilection for the Intertrochanteric Region of the Femur Radiology 212, 693-698
[2] Ragsdale BD (1993) Polymorphic fibro-osseous lesions of bone: an almost site-specific diagnostic problem in the proximal femur Hum Pathol 24:505-512
[3] Heim-Hall JM, Williams RP (2004) Liposclerosing myxofibrous tumour: A traumatized variant of fibrous dysplasia? Report of four cases and review of the literature Histopathology 2004;45:369-76
[4] Milgram JW (1990) Malignant transformation in bone lipomas Skeletal Radiol 19:347-352
[5] Ragsdale BD, Sweet DE (1989) Radiology as gross pathology in evaluating chondroid lesions Hum Pathol 20:930-951
Citation
J McNamee, G Briggs, D Gracey.
Musgrave Park Hospital,
Stockman’s Lane, Belfast,
Norther Ireland BT9 7JB (2012, Jul. 17)
Liposclerosing Myxofibrous Tumour {Online}
URL: http://www.eurorad.org/case.php?id=10137