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| LETTER TO THE EDITOR |
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| Year : 2014 | Volume
: 1
| Issue : 2 | Page : 165-166 |
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Cardinal characteristics of lipoma arborescens
Binit Sureka, Brij Bhushan Thukral, Mahesh Kumar Mittal
Department of Radiodiagnosis and Imaging, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India
| Date of Web Publication | 31-Jul-2014 |
Correspondence Address:
Dr. Binit Sureka
Department of Radiodiagnosis and Imaging, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi - 110 029
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2349-0977.137868
How to cite this article:
Sureka B, Thukral BB, Mittal MK. Cardinal characteristics of lipoma arborescens. Astrocyte 2014;1:165-6 |
Sir,
Lipoma arborescens is a chronic nonneoplastic process affecting the synovial joints, and is characterized by adipose tissue deposition in the subsynovial space. It may be associated with joint effusion or a synovial cyst.
Lipoma arborescens also known as "villous lipomatous proliferation of synovial membrane" was first described by German surgeon, Albert Hoffa in 1904. The Latin word arborescens means "tree-forming or tree-like". Any synovial joint can be involved like glenohumeral joint, elbow, hip, ankle but the most commonly involved joint is the knee joint. Bilateral involvement has also been described. The suprapatellar pouch is the most commonly involved site within the knee joint. According to Vilanova et al.,[1] lipoma arborescens is of two types - primary type, which is idiopathic typically affecting younger patients, and a much more common secondary variety affecting older patients with coexisting inflammatory arthritis.
Pathologically, lipoma arborescens is a benign chronic process in which subsynovial space is replaced with fronds like mature adipose tissue. [2] Secondary type may show infiltration of synovial lining with chronic inflammatory cells.
Patients may present with joint swelling of insidious onset, pain, stiffness, secondary osteoarthritis, or as an inflammatory arthropathy.
On imaging, plain radiographs may show obliteration of suprapatellar fat with radiolucent areas suggestive of fat. Secondary osteoarthritic changes with marginal erosions may be encountered. On ultrasound, hyperechoic, soft frond-like masses are seen, which bends and waves in real time during joint manipulation. On computed tomography (CT), fatty attenuation frond-like structures are seen with joint effusion, which is characteristic. On magnetic resonance imaging (MRI), these frond-like structures show signal intensity similar to that of fat on all pulse sequences and on short tau inversion recovery (STIR) sequences or presaturation of the fat, these masses show signal suppression [Figure 1]. No magnetic susceptibility effects are seen, which are characteristic of hemosiderin deposition. No enhancement is seen on postcontrast images unless there is existing synovial inflammation. [3],[4] | Figure 1: (a) X-ray knee showing swelling in suprapatellar region with lucent (arrows) projections. (b, c) Coronal T1-weighted and STIR MRI image showing hyperintense fronds (arrow) with suppression of signal (black arrow) with joint effusion. (d) CT showing joint effusion, fat density (arrow). (e) Ultrasound showing hyperechoic fronds (arrow) with joint effusion. (f) CT image showing joint effusion (black arrow) with fat (white arrow). (g, h) Axial T1-weighted and STIR MRI image showing hyperintense fronds (white arrow) and joint effusion with suppression of fat signal (black arrow).
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The differentials of lipoma arborescens include pigmented villonodular synovitis (PVNS), synovial osteochondromatosis, rheumatoid arthritis, synovial lipoma, and synovial hemangioma. [3],[4] PVNS, due to hemosiderin deposition, shows low signal intensity in the synovium on both T1- and T2-weighted sequences with paramagnetic effect of hemosiderin on gradient-echo sequences. Synovial osteochondromatosis shows typical osteoid and chondroid calcifications, which are oval shaped well defined lesions showing low signal on all pulse sequences. Synovial hemangioma shows intense enhancement and calcified phleboliths within. Rheumatoid arthritis involves bilateral joints, shows synovial thickening, bony erosions, and on MRI shows decreased signal intensity on T2-weighted images in the synovium due to fibrous pannus formation. Synovial lipoma is an important differential and must be differentiated from lipoma arborescens. Synovial lipoma is a well-defined round or oval-shaped lesion without synovial changes.
Treatment of choice is synovectomy. Recurrence after treatment is rare.
| References | |  |
| 1. | Vilanova JC, Barceló J, Villalón M, Aldomà J, Delgado E, Zapater I. MR imaging of lipoma arborescens and the associated lesions. Skeletal Radiol 2003;32:504-9. 
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| 2. | Hallel T, Lew S, Bansal M. Villous lipomatous proliferation of synovial membrane(lipoma arborescens). J Bone Joint Surg 1988;70:264-70.
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| 3. | Venkatanarasimha N, Suresh SP. AJR Teaching File: An uncommon cause of knee swelling. AJR Am J Roentgenol 2009;193:S53-5.
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| 4. | Coll JP, Ragsdale BD, Chow B, Daughters TC. Lipoma arborescens of the knees in a patient with Rheumatoid arthritis. Radiographics 2011;31:333-7.
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[Figure 1]
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