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Salem Health: Cancer Liposarcomas Category: Diseases, symptoms, and conditions Also Known As: Soft-tissue liposarcoma Related Conditions: Soft-tissue sarcomas Definition Liposarcoma is the second most common malignant soft-tissue sarcoma in adults after malignant fibrous histiocytoma (MFH). Liposarcoma, a mesenchymal sarcoma, accounts for between 12 percent and 18 percent of all malignant soft-tissue tumors and usually manifests as a nonspecific soft-tissue mass. Frequently the fat it contains is not radiographically detectable. Liposarcoma demonstrates a wide range of manifestations and prognoses, ranging from a well-differentiated nonmetastasizing neoplasm with good prognosis to a high-grade sarcoma with hematogenous metastases to the lung and the visceral organs. Risk Factors A relationship to trauma has been reported. The myxoid and round cell type of liposarcoma are associated with a reciprocal translocation between chromosomes 12 and 16. Etiology and the Disease Process Liposarcoma is a malignant tumor of mesenchymal origin with the microscopic appearance of adipose tissue, although in some cases it does not contain visible fat. It is made up of several cell types. The well-differentiated type of liposarcoma, which has the best prognosis, has mature lipocytes with varying degrees of nuclear atypia. It is seen in only 15 percent of cases. The most common type, accounting for 40 percent to 50 percent of all liposarcomas, is the myxoid type, which is composed of proliferating fibroblasts with less than 10 percent fat. This type of tumor often metastasizes to serosal and pleural surfaces, subcutaneous tissue, and bone. The pleomorphic type is seen in approximately 20 percent of cases and is a highly anaplastic tumor with pleomorphic (many sized and shaped) cells growing in a disorderly fashion. The round cell type is seen in less than 10 percent of cases, is poorly differentiated, and is often associated with hemorrhage and necrosis. It is highly cellular, composed of primitive small round cells. Retroperitoneal liposarcoma is a slow-growing variant that rarely metastasizes and usually displaces rather than infiltrates or invades surrounding tissues. Incidence Liposarcomas represent between 12 percent and 18 percent of all malignant soft-tissue tumors. Annually 2.5 cases occur per 1 million population. Symptoms Liposarcoma usually manifests as a large, painless mass between 2 and 30 centimeters (cm) in size, associated with weight loss in a patient between the ages of fifty and sixty. It is slightly more common in men than in women. Liposarcoma can be painful in 15 percent of patients because of the compression of the adjacent neurovascular bundle or adjacent abdominal organs. Retroperitoneal tumors can weigh several pounds. Screening and Diagnosis Liposarcomas are best diagnosed by magnetic resonance imaging (MRI) with gadolinium intravenous contrast. The tumor appears as a large hypervascular septated mass containing fat and soft tissue. In contradistinction to a lipoma, liposarcoma enhances with intravenous contrast. Liposarcoma can have large areas of necrosis and hemorrhage and can be located in the trunk or retroperitoneum in approximately 42 percent of cases, in the lower extremity in 41 percent of cases, in the upper extremity 11 percent of the time, and in the head and neck in 6 percent, with predilection for the thigh and retroperitoneum. The more differentiated the tumor, the closer the signal characteristics of the tumor approach that of fat. Myxoid and pleomorphic tumors may demonstrate little or no fat on computed tomography (CT). On nuclear medicine positron emission tomography (PET) scans, the tumor is fluorodeoxyglucose (FDG) avid. According to the World Health Organization classification, liposarcoma includes well-differentiated, myxoid, pleomorphic, and round cell types, with the most common type being the myxoid type (50 percent of all liposarcomas). Myxoid liposarcoma can appear benign on MRIs. These gelatinous lesions can demonstrate a cystlike appearance. High-grade liposarcoma often contains no recognizable fat and as such is indistinguishable from other soft-tissue malignancies. As with most malignant musculoskeletal tumors, surgical staging depends on pathology, compartmentalization, and presence or absence of metastases:  Stage Ia: Low grade, intracompartmentalStage Ib: Low grade, extracompartmentalStage IIa: High grade, intracompartmentalStage IIb: High grade, extracompartmentalStage IIIa: Low or high grade, intracompartmental,presence of metastasesStage IIIb: Low or high grade, extracompartmental,presence of metastasesTreatment and Therapy The treatment depends on the stage at diagnosis. Stage I lesions are handled with surgical resection with wide margins. Stage II lesions are treated with more radical resection, possible amputation, and radiation therapy. Therapy for Stage III lesions includes surgical resection with radiation and chemotherapy. Prognosis, Prevention, and Outcomes The well-differentiated type of liposarcoma has the best prognosis, with overall five-year survival rates exceeding 80 percent. However, even with the well-differentiated type, there can be local recurrence. The well-differentiated type rarely metastasizes, unlike the pleomorphic and round cell types, which metastasize and have a five-year survival rate of only 50 percent. A size greater than 15 cm connotes a poor prognosis. Retroperitoneal liposarcoma is the most radiosensitive of all soft-tissue sarcomas, with an overall five-year survival of 32 percent. Debra B. Kessler, M.D., Ph.D. For Further InformationCotran, Ramzi S., Vinay Kumar, and Stanley L. Robbins, eds. Robbins Pathologic Basis of Disease. 5th ed. Philadelphia: W. B. Saunders, 1994. Bergquist, Thomas H. MRI of the Musculoskeletal System. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2001. Stoller, David W. Magnetic Resonance Imaging in Orthopedics and Sports Medicine. Philadelphia: J. B. Lippincott, 1993. Stoller, David W., et al. Diagnostic Imaging: Orthopedics. Salt Lake City, Utah: Amirsys, 2006. Other Resources The Liddy Shriver Sarcoma Initiative Liposarcoma http://liddyshriversarcomainitiative.org/Newsletters/V01N05/Liposarcoma/liposarcoma.htm Sarcoma Foundation of America http://www.curesarcoma.org See Also Breast cancers; limb salvage; malignant tumor; obesity-associated cancers; sarcomas, soft-tissue. |
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