Dedifferentiated liposarcoma of the subcutis

This report describes an 82-year-old woman with dedifferentiated liposarcoma, an extremely rare neoplasm of the subcutis. The patient had first recognized a very soft mass in the anterolateral part of the right thigh more than 20 years earlier, but because the tumor showed little change over this period, she did not seek treatment. She recently noticed a hard, rapidly growing mass within the former tumor. Both magnetic resonance imaging and axial computed tomography revealed a subcutaneous fatty lesion measuring 12 x 7 x 4 cm and a well-delineated mass-like area (4 x 3 x 3 cm) of nonfatty tissue within the lesion. Histologically, the former was a mature lipomatous tumor with broad fibrous septa containing some atypical stromal cells, and the latter was a much more cellular, spindle cell tumor with a malignant fibrous histiocytoma-like pattern. The authors propose that dedifferentiated liposarcoma is not restricted to the deep soft tissues and may develop in the subcutis and further suggest appropriate surgical management for well-differentiated fatty tumors of subcutaneous origin.