Myxofibrosarcoma and Undifferentiated Pleomorphic Sarcoma

Both myxofibrosarcoma and undifferentiated pleomorphic sarcoma (UPS) are sarcomas that primarily occur in the extremities of older patients. UPS (previously known as malignant fibrous histiocytoma) is now considered a diagnosis of exclusion, representing a group of high-grade, heterogeneous tumors with no clear line differentiation and characterized by high rates of distant metastases. Myxofibrosarcoma (formerly myxoid variant of malignant fibrous histiocytoma) is a distinct histologic entity that is largely distinguished from UPS by its myxoid stroma and curvilinear vascular pattern. Myxofibrosarcoma tends to have a locally infiltrative behavior that can often be seen as T2 hyperintense “tails” on magnetic resonance imaging. Local recurrence rates can be as high as 61% and are independent of grade. Unlike other sarcomas, it is recommended that tumors be excised with at least a 2 cm margin around both clinically and radiographically evident tumor. Low-grade tumors do not tend to metastasize but can recur as high-grade tumors with increased metastatic potential. Surgery is the mainstay of treatment for localized disease. For high-grade tumors, this may require complex plastics and vascular reconstruction. Selecting cases for multimodality therapy, including radiation and chemotherapy, should be done on a case-by-case basis after review by a multidisciplinary sarcoma team with particular attention to a patient’s risk of local recurrence and distant metastases. Further studies into histology-specific therapeutic targets will help inform future clinical trials. This review contains 4 figures, 4 tables and 54 references Key words: chemotherapy, distant metastases, extremity sarcoma, local recurrence, malignant fibrous histiocytoma, myxofibrosarcoma, radiation, sarcoma, surgical margins, T2 hyperintense tails, undifferentiated pleomorphic sarcoma