CASE 15421 Published on 06.02.2018

Lipoma arborescens in an adolescent

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Mahesh Chaudhary, Leela Chaudhary, Md. Monir Uddin, Sharzia Asma–Ul Hosna, Bishwajit Bhowmik

Bangabandhu Sheikh Mujib Medical University (BSMMU),
Department of Radiology & Imaging;
Dhaka, Bangladesh;
Email:maheshchaudhary@hotmail.com
Patient

19 years, male

Categories
Area of Interest Musculoskeletal joint ; Imaging Technique MR
Clinical History
A 19-year-old male adolescent presented with a swelling of the left knee joint for 2 years with restricted movement for 2 months. There was no history of trauma.
Imaging Findings
Magnetic Resonance Imaging (MRI) revealed a frond-like intra-articular mixed signal intensity lesion in the anterior aspect of the left knee joint, predominantly hyperintense in T1-weighted image (T1WI), less hyperintense in T2-weighted image (T2WI) and proton density image (PDI). On short T1 inversion recovery (STIR) sequences it showed signal suppression. After intravenous contrast, no appreciable enhancement was noted. There was mild joint effusion.
Discussion
Lipoma arborescens is one of the rare intra-articular lesions which is caused by inflammation of synovial fluid with deposition of mature fatty components within them. [1, 2] This term was first coined by Hoffa and was elaborated in detail by Arzimanoglu. [3, 4] The Latin term arborescens refers to the leafy appearance of a tree similar to that of a frond. [5] The anterior and superior aspect of the knee is most commonly affected, however, involvement of other appendicular joints is also reported in the literature. [5, 6, 7, 8]

The infiltration of mononuclear cells leads to an inflammatory reaction, causing hypertrophy of the synovium and deposition of mature lipocytes, showing a frond-like appearance. [9]

Magnetic Resonance Imaging (MRI) is the modality of choice for radiological diagnosis of lipoma arborescens. [10] It shows high signal intensity in T1WI, is less hyperintense in T2WI and hypointense on fat-suppressed sequences. [9, 11]
Computed tomography (CT) reveals a non-enhancing, low density, frond-like intra-articular mass. [12]
On ultrasonography (USG) a lobulated hyperechoic mass is seen mostly associated with a variable amount of joint effusion. [13]
Plain X-ray films may demonstrate feathery fatty lucency within a joint with joint effusion and bony erosion. [11]

This condition is usually benign and asymptomatic, however, synovectomy is indicated for patients with persistent pain. [9]

Lipoma arborescens is one of the rare intra-articular benign lesion, characterised by synovial proliferation with frond-like deposition of mature fatty components. MRI is the best radiological diagnostic tool for pre-operative evaluation. Although it is very uncommon, it can be one of the causes of chronic large joint swellings, especially of the knee joint. Synovectomy is indicated for symptomatic patients.
Differential Diagnosis List
Lipoma arborescens
Pigmented villonodular synovitis (PVNS)
Synovial osteochondromatosis
Synovial haemangioma
Loose bodies
Final Diagnosis
Lipoma arborescens
Case information
URL: https://www.eurorad.org/case/15421
DOI: 10.1594/EURORAD/CASE.15421
ISSN: 1563-4086