Myxoid liposarcoma of right popliteal fossa: Case report and review.

RATIONALE: Myxoid liposarcoma (MLS) accounts for 30% of liposarcomas and typically arises in the thigh, but rarely arises in the popliteal fossa. Managing giant, neurovascular-abutting MLS in young adults is poorly characterized.

PATIENT CONCERNS: A 35-year-old man presented with a right popliteal mass growing over > 6 years, accompanied by progressive swelling and incomplete flexion of the right knee. He denied smoking, denied alcohol use, and had no family history of malignancy.

DIAGNOSES: magnetic resonance imaging showed a 179 × 154 × 99 mm multilocular cystic-solid lesion abutting/partly encasing the popliteal vessels and contacting the sciatic/common peroneal nerves. Preoperative cytology suggested benignity; definitive resection revealed MLS grade II with 20% round cell component (R1 margin adjacent to the vessel plane).

INTERVENTIONS: En bloc resection with function-preserving R1 margins was performed given neurovascular involvement; popliteal artery/vein and nerves were preserved. Postoperative external-beam radiotherapy was delivered to 60 Gy in 30 fractions (2 Gy/fraction).

OUTCOMES: At the 18-month follow-up, progressive recovery of knee joint range of motion was observed, and no local recurrence or metastasis at 18 months. Magnetic resonance imaging at 6 and 18 months showed no local-recurrence or metastasis.

LESSONS: This case demonstrates that in young patients with popliteal MLS closely related to neurovascular structures, function-preserving R1 resection plus postoperative 60 Gy can achieve local-control while maintaining limb function, provided meticulous technique and guideline-concordant surveillance.