liposarcoma

Liposarcoma is a malignant tumor that arises from adipocytes or fat-forming cells and is the most common type of soft tissue sarcoma in adults. It typically presents as a slow-growing, painless mass in the extremities, trunk, or retroperitoneum. Tumors in the retroperitoneum can become large before symptoms appear and may cause compressive symptoms.

The major histologic subtypes are well-differentiated liposarcoma (WDLS), dedifferentiated liposarcoma (DDLS), myxoid liposarcoma, pleomorphic liposarcoma, and round cell liposarcoma (the latter two representing higher-grade disease). WDLS and DDLS share a common tendency toward amplification of MDM2 and CDK4 genes. Myxoid liposarcoma often contains specific translocations, most commonly t(12;16)(q13;p11) producing FUS-CHOP (FUS-DDIT3), and less frequently t(12;22)(q13;q12) producing EWSR1-DDIT3.

Diagnosis relies on imaging and biopsy. MRI or CT helps define the extent and anatomic relations, while histologic examination confirms subtype. Molecular testing for MDM2 and CDK4 amplification supports WDLS or DDLS, and testing for FUS-CHOP or EWSR1-CHOP fusions supports myxoid liposarcoma.

Treatment is guided by subtype and stage. Localized disease is typically treated with surgical excision aiming for negative margins; adjuvant radiotherapy is often used, especially for extremity and retroperitoneal tumors, to reduce local recurrence. Chemotherapy regimens (commonly doxorubicin and ifosfamide) are used in higher-risk or advanced cases and vary by subtype; myxoid liposarcoma is relatively more chemosensitive and radiosensitive than other subtypes. Targeted therapies and clinical trials are areas of ongoing research.

Prognosis varies by histologic subtype and stage. WDLS generally has a lower risk of distant metastasis but a higher risk of local recurrence, while DDLS and pleomorphic liposarcoma carry a higher risk of metastasis and poorer outcomes. Long-term prognosis depends on tumor size, location, grade, and response to treatment.