High-grade intra-articular liposarcoma of the knee
Daniel A. Shaerf
Received: 21 September 2010 / Revised: 1 November 2010 / Accepted: 10 November 2010 / Published online: 21 December 2010
Abstract A high-grade pleomorphic intra-articular liposar-
coma of the knee is described in a 48-year-old man, which
was diagnosed histologically after arthroscopy of the knee
for suspected pigmented villonodular synovitis (PVNS).
The patient proceeded to undergo an extra-articular resec-
tion with a custom-made prosthesis. This report highlights
the need to remember this rare tumour in the differential
diagnosis of atypical soft tissue lesions within the knee joint
prior to instrumentation.
Soft tissue neoplasm
Soft-tissue swelling around the knee is a common clinical
entity. Soft tissue sarcoma (STS), on the other hand, is a
relatively rare finding. Liposarcoma is the second most
common type, accounting for around 16% of all STS .
The pleiomorphic variant is the rarest form of liposarcoma,
constituting just 5% of liposarcomas. It is paramount to
maintain a high index of suspicion, especially when either
the presentation or the imaging is not characteristic of a
benign condition, as the consequences of delayed or
misdiagnosis can be severe. We describe the case of a 48-
year-old man who presented with a soft-tissue swelling
around the knee that transpired to be an intra-articular,
high-grade pleomorphic liposarcoma.
A 48-year-old man presented to his local orthopaedic
surgeon with a painful knee associated with lateral joint
line swelling. He underwent MRI, which showed a medial
meniscal tear and a large, multifocal, intra-articular soft-
tissue mass, involving the whole of the synovial space and
was almost entirely intra-articular. The mass had interme-
diate signal intensity (SI) on T1-weighted spin echo and fat-
suppressed proton density-weighted fast spin echo images.
There was a very small focal penetration of the lateral joint
capsule. The tumour showed no evidence of fatty differen-
tiation and was associated with moderate joint effusion. No
bone erosion was demonstrated (Fig. 1).
The lesion was interpreted as being due to pigmented
villonodular synovitis (PVNS) at the referring hospital and,
therefore, he underwent arthroscopy, which showed multi-
ple nodular fatty tissue elements that were excised using an
arthroscopic shaver. Histology of the excised tissue
revealed a high-grade spindle cell sarcoma with focal
scattered multivacuolated atypical lipoblasts, diagnostic of
pleomorphic liposarcoma. Molecular genetics were nega-
tive for the MDM2 gene.
Therefore, he was referred to the local Sarcoma Service,
where further imaging was performed, showing significant
intra-articular progression of the soft-tissue mass with further
extra-articular spread. Chest CT demonstrated multiple
pulmonary metastases. He underwent an extra-articular
resection of the knee joint with a custom-made rotating hinge
prosthesis replacing the distal femur and knee joint (Stanmore
Implants Worldwide, Elstree, UK; Fig. 2).
Histological examination of the resected specimen
confirmed an intra-articular pleomorphic liposarcoma
The patient concerned gave full informed consent to his information
being submitted for publication
D. A. Shaerf (*)
The London Sarcoma Service,
Royal National Orthopaedic Hospital,
Stanmore, Middlesex HA7 4LP, UK
Skeletal Radiol (2011) 40:363–365