Dedifferentiated liposarcoma.

Dedifferentiated liposarcoma is a high-grade nonlipogenic sarcoma that arises in a background of a preexisting well-differentiated liposarcoma. The phenomenon of dedifferentiation is time dependent, and primary or de novo tumors exceed secondary neoplasms in a ratio of 9:1. The tumor occurs most frequently in adults beyond the 6th decade of life, slightly predominates in men, and involves the abdominal cavity most often. Pleomorphic malignant fibrous histiocytoma-like histologic features are the most commonly observed phenotype, although other sarcomatous phenotypes have been described less frequently. Surgical treatment is the main form of therapy for dedifferentiated liposarcoma, which is associated with a reported local recurrence rate of 41% to 52%, 15% distant metastatic rate, and 30% disease-related mortality rate. On a chromosomal level, dedifferentiated liposarcoma frequently displays the same chromosomal abnormality associated with well-differentiated liposarcomas--ie, the presence of a supernumerary ring or giant chromosome derived from the 12q(13-15) region.