Contributed by L. Chinsoo Cho, MD, MS
Myxoid liposarcoma represents a distinct subgroup of liposarcomas with unique clinical and pathologic features. Treatment employs a multidisciplinary approach, and surgery with or without radiation therapy is the usual therapy. About 40% of patients with the condition relapse and require additional treatment.1 Outcomes can be improved with preoperative radiotherapy, a treatment that also lessens radiation dose and reduces long-term radiation complications.2
A 50-year-old man sought medical care for a slowly enlarging mass in his leg. He had had aching pain in the left thigh for more than a year that he initially attributed to a possible work-related injury. The patient sought further medical evaluation when the mass did not dissipate and began to enlarge.
A University of Minnesota Health orthopedic oncologist examined the patient and found a greater than 30 cm mass in the left medial thigh and limitations of left leg and foot extension and flexion. Initial MRI of the left lower extremity revealed a 17 x 18 x 24 cm mass. The tumor was a well-circumscribed, heterogeneous soft-tissue mass in the medial compartment of the left thigh. A core-needle biopsy revealed a myxoid liposarcoma. Immunohistochemical staining revealed tumor cells focally positive for S100 protein and negative for EMA, SMA and CK AE1/AE3. Fluorescent in situ hybridization (FISH) was performed on paraffin-embedded slides of the left thigh mass. Use of a molecular probe for DDIT3 (12q13) showed rearrangements of DDIT3 gene and confirmed the diagnosis.
The patient’s case was discussed at the University of Minnesota’s interdisciplinary sarcoma tumor board, and the consensus recommendation was for neoadjuvant radiotherapy followed by surgical resection. The radiotherapy-planning CT scan revealed a tumor volume of 4500 cc. The patient underwent 5 weeks of preoperative radiotherapy (total dose of 50 Gy in 2 Gy fractions). The 3-dimensional external beam photon radiotherapy was done 5 days per week. MRI at 1 month follow-up showed a tumor of 4550 cc, slightly larger than the initial tumor. The patient underwent surgery 1 week after a post-radiotherapy MRI (5 weeks after completing the radiotherapy). Pathologic examination of the resected tumor showed extensive necrosis with 95% nonviable tumor. At 8 months postsurgery, the patient relapsed and required systemic therapy.
Unlike other soft tissue sarcomas, myxoid liposarcomas have shown pronounced pathologic responses to preoperative radiotherapy with a moderate dose of 50 Gy, although volumetric responses to radiotherapy have been less impressive.2 The volumetric measurements gathered in imaging studies, however, often underestimate the true pathologic response to pre-operative radiotherapy, as this case illustrates. Patients with sarcomas such as myxoid sarcomas that exhibit DDIT3 gene rearrangement should be considered for pre-operative radiotherapy as a standard management for the condition. This patient’s outcome with a relapse 8 months after surgery emphasizes the need for systemic as well as local management.
Sarcomas, including liposarcoma, present treatment challenges. Recent studies, however, are uncovering the possible benefits of presurgical radiotherapy and new methods for better identifying treatment.Continue reading