Synchronous Myxoid Liposarcoma of the Popliteal Fossa and Distal Femur Treated with Single-Session En Bloc Resection and Oncologic Endoprosthetic Reconstruction: A Case Report
Agustín Davies1*, Marcos Galli Serra1, Walter Parizzia1, Bruno Terrarossa Retegui1
1Orthopaedics and Traumatology Service, Hospital Universitario Austral, Buenos Aires, Argentina.
*Corresponding Author: Agustín Davies, Orthopaedics and Traumatology Service, Hospital Universitario Austral, Buenos Aires, Argentina.
https://doi.org/10.58624/SVOAOR.2026.06.031
Received: October 06, 2026
Published: October 25, 2026
Citation: Davies A, Serra MG, Parizzia W, Retegui BT. Synchronous Myxoid Liposarcoma of the Popliteal Fossa and Distal Femur Treated with Single Session En Bloc Resection and Oncologic Endoprosthetic Reconstruction: A Case Report. SVOA Orthopaedics 2026, 6:5, 235-241. doi: 10.58624/ SVOAOR.2026.06.031
Abstract
Background: Myxoid liposarcoma (MLS) is a soft tissue sarcoma with a distinctive tendency to metastasize to extrapulmonary sites, including soft tissue and bone. Synchronous lesions in soft tissue and bone are rare, and distinguishing multicentric primary tumors from metastatic spread is difficult. We report a case treated with single-session en bloc resection and oncologic endoprosthetic reconstruction.
Case Description: A 38-year-old man presented with a four-month history of a posterior knee mass. A liposarcoma diagnosed at another center was confirmed as MLS on review of the paraffin block at our institution, and baseline chest CT was negative. A subsequent MRI showed an intramedullary lesion in the ipsilateral distal femur, and CT-guided biopsy again showed MLS. After tumor board discussion, both lesions were resected in a single session: en bloc resection of the popliteal mass in the prone position, followed by a 10-cm distal femoral resection and reconstruction with a cemented modular oncologic endoprosthesis in the supine position. Margins were negative in both specimens. Pulmonary lesions appeared two months after surgery, and the patient continues oncologic treatment. At 12 months he had no pain, and knee flexion was limited to 15°. Molecular studies in the literature indicate that multifocal MLS reflects metastatic spread rather than independent primary tumors. Clonality was not tested in our patient, so we regard the synchronous presentation as probable metastasis of one lesion to the other site.
Conclusions: Synchronous soft tissue and bone MLS should be approached as probable metastatic disease, with whole-body staging, molecular confirmation of clonality when possible, and management in a specialized sarcoma center. Single-session limb salvage was technically feasible and achieved negative margins, but at a functional cost, and early pulmonary progression underlines the aggressive biology of the disease.
Keywords: Myxoid Liposarcoma; Multifocal Liposarcoma; Bone Metastasis; Endoprosthetic Reconstruction; Popliteal Fossa; Limb Salvage