Dedifferentiated liposarcoma with features of rhabdomyosarcoma.

We describe a case of recurrent dedifferentiated retroperitoneal liposarcoma with light microscopy features of rhabdomyosarcoma, the first such reported case. The tumor contains a pleomorphic pattern consisting of plump fusiform cells, tadpole cells, malignant appearing lipoblasts, and other nondescript bizarre cells. Of particular interest is a number of tumor cells with plump, bizarre nuclei which contain cross-striations of skeletal muscle pattern. The literature on dedifferentiated liposarcoma is reviewed, and the significance of this case in terms of a current model of mesenchymal differentiation is discussed, with particular attention to the postulate of a common precursor for a variety of soft-tissue tumor histologies.