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WHO Classification of Tumours
Myxoid liposarcoma
Connective, subcutaneous and other soft tissues


Myxoid liposarcoma (MLS) is a malignant tumour histologically characterized by round to oval mesenchymal cells, small signet ring lipoblasts, and a rich network of capillaries in a myxoid stroma. Included in this category are lesions formerly known as round cell liposarcomas (which lack a myxoid stroma, but are otherwise identical; myxoid and round cell subtypes are interpreted as histological continuum).
In more than 90% of MLS patients, the translocation (12;16)(q13;p11) can be detected. The resulting fusion of the genes DDIT3 and FUS is highly sensitive and specific for MLS.
MLS are well-circumscribed, multinodular intramuscular tumours which preferentially arise in the deep soft tissues of the extremities, particularly in the musculature of the thigh. They affect predominantly young adults (peak incidence in the 4th and 5th decades of life). The tumour tends to recur locally; distant metastases develop in one-third of patients, often in unusual soft tissue or bone (particularly the spine) sites, even before spread to the lungs. Factors predicting an unfavourable outcome are high histological grade, presence of necrosis, and TP53 overexpression; the prognosis for multifocal MLS is always poor

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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002