The clinicopathologic significance and histopathologic classification of liposarcoma are well delineated in previous studies, but the literature on recurrent dediffenentiated liposarcoma is rare. We described a case of recurrent dedifferentiated retroperitoneal liposarcoma with light microscopy features of rhabdomyosarcoma. This loss of one cell-specific marker and gain of another is termed the ”antigenic shift” phenomenon and appeared to foretell the emergence of a true second phenotype. 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.