Contributor: Gordon K. Klintworth
The liposarcoma is highly malignant common soft tissue sarcoma composed of lipoblasts in various stages of differentiation. The neoplasm is believed to arise from primitive mesenchymal cells, rather than from mature adipose connective tissue. Liposarcoma occurs most often in the thigh and retroperitoneum and involves the orbit on rare occasions. The light microscopic appearance of the tumor varies considerably from tumor to tumor, but also within different parts of the same neoplasm. The tumor cells contain lipid and some of them are round and have a vacuolated cytoplasm in routinely processed tissue. Variants of the liposarcoma include the myxoid liposarcoma [liposarcoma - myxoid], round cell liposarcoma [liposarcoma - round cell], pleomorphic liposarcoma [liposarcoma - pleomorphic],  dedifferentiated liposarcoma [liposarcoma - dedifferentiated] and well-differentiated liposarcoma [liposarcoma - well-differentiated].. The cause is usually unknown, but a chromosome translocation syndrome involving the CHOP and FUS genes between human chromosomes 12 and 16 [t(12;16)(q13;p11)] has been found in the myxoid liposarcoma and round cell liposarcoma. The risk of metastatic dissemination relates to the degree of nuclear atypia, hyperchromatism, anaplasia and mitotic activity. The presence of cytoplasmic fat can be identified in frozen tissue sections stained with Oil red O and other stains for lipid. The differential diagnosis includes other malignant neoplasms, which may also contain lipid. As a rule liposarcoma is a neoplasm of adults, but rarely it may affect children.
When present in the orbit the recommended treatment for a myxoid liposarcoma is a wide resection, but an exenteration may be necessary to prevent recurrence. Regardless of therapy there is a high risk of distant metastases.