J Korean Soc Radiol.  2010 Dec;63(6):561-564.

MRI Findings of Synovial Lipoma Arborescens of the Hip: A Case Report

• Park HJ
• Park SI
• Park CS
• Kim MS
• Park NH
• Park JH
• Yi SY

Abstract

Lipoma arborescens is a rare intra-articular lesion consisting of villous lipomatous proliferation of the synovium that tends to occur in the knee joint, especially in the suprapatellar pouch. The lesion has been observed in other locations, including the glenohumeral joint, subdeltoid bursa, hip, and elbow. We report a case of a lipoma arborescens of a unilateral hip joint in a 34-year-old man. MRI and a whole body bone scan were performed. In addition, a surgical synovectomy was performed and microscopic examination of the tumor revealed multiple variable-sized villous masses composed of mature fat tissue and lined by synovial cells which confirmed the diagnosis of lipoma arborescens.

MeSH Terms

Adult
Elbow
Hip
Hip Joint
Humans
Knee Joint
Lipoma
Magnetic Resonance Imaging
Shoulder Joint
Soft Tissue Neoplasms
Synovial Membrane

Figure

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  Fig. 1 Plain radiograph reveals joint space narrowing and erosive changes in the inferomedial portion of the right femoral head, but no gross calcification. Extrinsic indentation in the medial aspect is also noted.

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  Fig. 2 Axial T1-weighted (A) and T2-weighted (B) MR images of the right hip show the frond-like villous lipomatous proliferation of the synovium with signal corresponding to the fat (arrow). A coronal T2-weighted fat-suppressed MR image (C) shows decreased signal intensity of synovial proliferation identical to that of subcutaneous fat (arrow).

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  Fig. 3 A whole body bone scan (30 mci of Tc-99m MDP) shows increased uptake in the right hip joint.

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  Fig. 4 Microscopic examination of the tumor reveals villous masses composed of mature adipocytes lined by synovial cells (×40, inlet ×200).

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