• 2/3 of cases arise in dermal/subcutaneous tissues
• Local, often repeated, recurrences in up to 50-60% of cases (unrelated to histologic grade)
• Intermediate- and high-grade malignant neoplasms may develop metastases in 30-35% of cases
Macroscopic
• Superficially located neoplasms consist of multiple variably gelatinous or firmer nodules
• Deep-seated neoplasms often present as single mass with myxoid cut surfaces
Microscopic
• Broad spectrum of cellularity, cytologic atypia, and proliferative activity reflected by 3 grades of malignancy
• Multinodular growth, spindled and stellate atypical fibroblastic cells
• Myxoid stroma with elongated, curvilinear, thin-walled vessels
• Often pseudolipoblasts are present
Top Differential Diagnoses
• Myxoid dermatofibrosarcoma protuberans
• Myxoid liposarcoma
• Low-grade fibromyxoid sarcoma (Evans tumor)
• Myxoinflammatory fibroblastic sarcoma
• Myxoid malignant peripheral nerve sheath tumor
Gross Photograph of Myxofibrosarcoma A case of low-grade myxofibrosarcoma is shown with myxoid, gelatinous cut surfaces. (Courtesy T. Mentzel, MD.)
Superficial Myxofibrosarcoma Scanning magnification view shows a superficial, low-grade myxofibrosarcoma involving the subcutis and deep dermis. Numerous elongated, thin vessels are easily identified in a prominent myxoid stroma.
Myxofibrosarcoma With Cellular and Myxoid Areas Myxofibrosarcoma is characterized by a variable cellularity and is composed of atypical fibroblastic cells that are set in a prominent myxoid stroma with numerous elongated curvilinear vessels .
High-Grade Myxofibrosarcoma This more cellular neoplasm is composed of atypical, epithelioid-shaped tumor cells with abundant eosinophilic cytoplasm and round, vesicular nuclei. This case represents a rare epithelioid cell variant of myxofibrosarcoma.
TERMINOLOGY
Abbreviations
• Myxofibrosarcoma (MFS)
Synonyms
• Myxoid malignant fibrous histiocytoma
Definitions
• MFS represents spectrum of malignant fibroblastic neoplasms with variably myxoid stroma and characteristic elongated curvilinear vessels
CLINICAL ISSUES
Epidemiology
• Incidence
1 of most common sarcomas in elderly patients
• Age
Affects mainly patients in 6th-8th decades
Exceptionally rare in patients < 20 years old
• Sex
Slight male predominance
Site
• Majority arise in limbs and limb girdles
Lower > upper extremities
• Rarely on trunk, head and neck region
• Very rarely on hands and feet
• 2/3 of cases arise in dermal/subcutaneous tissues
Presentation
• Painless mass
• Slow growing
Treatment
• Surgical approaches
Complete and wide excision
Prognosis
• Local, often repeated, recurrences in up to 50-60% of cases (unrelated to histologic grade)
• Low-grade MFS usually does not metastasize
• Low-grade MFS may show tumor progression in subsequent recurrences
• Intermediate- and high-grade MFS may develop metastases in 30-35% of cases
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are easily identified in a prominent myxoid stroma.
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