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Soft Tissue Tumors
Well differentiated myxoid liposarcoma
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)
Revised: 17 June 2009, last major update June 2009
Definition
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● Low grade tumor with primitive non-lipogenic mesenchymal cells, signet ring lipoblasts and prominent myxoid stroma with branching vascular pattern
Terminology
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● Also called paucicellular myxoid liposarcoma
Epidemiology
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● Peaks in 30’s and 40’s
● May occur in children
Sites
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● Usually thigh and lower extremity of young adults
● Retroperitoneal involvement is rare
Case reports
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● Young men with multicentric tumors (World J Surg Oncol 2007;5:139)
Treatment and prognosis
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● Median survival 105 months (Ann Surg Oncol 2007;14:1507)
● Pure tumors (without round cells) have low grade behavior with only rare metastases
● Poorer prognosis if round or pleomorphic cells
Gross images
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Gelatinous cut surface Tumor of popliteal region Distal thigh tumor of
(M-myxoid, arrow-adipose) 16-year-old boy
57-year-old man with cyst-like
tumor in subcutis of thigh
Other images: well circumscribed white tumor; lobulated gray-white tumor within skeletal muscle
Micro description
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● Low grade and paucicellular with monomorphic, stellate or fusiform cells without atypia
● Prominent chicken wire vasculature (delicate thin walled arborizing and curving capillaries)
● Numerous signet ring lipoblasts, particularly at periphery of lobules, has mucoid matrix rich in hyaluronidase sensitive acid mucopolysaccharides, may have large mucoid pools
● Lymphangioma-like cystic degeneration is relatively specific; rarely metaplastic cartilage or cartilage with TLS-CHOP fusion gene (Appl Immunohistochem Mol Morphol 2007;15:477)
● No/rare mitotic figures
Micro images
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Small back to back fat cells Large (mature) and
small fat cells
Resembles pulmonary edema Large irregular cystic spaces Cystic spaces with granular
eosinophilic material
Hypocellular around Large hypocellular zones Transition between cellular
a small artery around veins and hypocellular areas
Cords of cells resembling Hyalinized collagenous stroma (rare)
myxoid chondrosarcoma
Lipoblasts, myxoid stroma and branched capillaries
Lipoblasts, myxoid stroma and branched capillaries
Signet ring lipoblasts
Metastases to heart Metastases to thoracic epidural space
Other images: lipoblasts, myxoid stroma and branched capillaries #1; #2; #3; lipoblasts #1; #2; #3; #4
Cytology description
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● Myxoid material with arborizing blood vessels and lipoblasts (Acta Cytol 2007;51:456)
Positive stains
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● Vimentin, S100, CD36 (AJCP 1995;103:20)
Electron microscopy
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● White adipose tissue, aggregates of 60-Angstrom intermediate filaments and large masses of glycogen (AJCP 1979;72:521)
● Cells have investing basal lamina, pinocytotic vesicles, cytoplasmic glycogen and cytoplasmic lipid (AJSP 1980;4:163)
● Resembles lipoblastoma
Differential diagnosis
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● Extraskeletal myxoid chondrosarcoma - malignant chondrocytes, no cytoplasmic fat vacuoles, no prominent vasculature
● Lipoblastoma - similar histology but age 5 years or less
● Myxofibrosarcoma - older adults, often superficial, infiltrative, no cytoplasmic fat vacuoles, more nuclear atypia, thicker curvilinear vessels, frequent mitotic figures
● Myxoma - extremely paucicellular, lacks a prominent vascular component
End of Soft Tissue Tumors > Well differentiated myxoid liposarcoma
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