Myxoid liposarcoma with transition to round-cell lesion-cell cycle regulator genes and telomerase activity characterizing tumor progression: A case report

A mixed myxoid/round cell liposarcoma was macrodissected in its 2 histologi c components and investigated for genetic differences between its low-grade myxoid and the high-grade round-cell region. For both, we failed to detect p53 gene mutations, loss of heterozygosity at the p53 or Rb genes, and p53 protein expression. The round-cell component showed a high telomerase acti vity, and an elevated c-myc mRNA and protein expression. The myxoid compone nt was characterized by a lack of telomerase activity and low c-myc mRNA ex pression, and immunohistochemistry failed to detect the c-myc protein. Ther e was a higher Mib-1 proliferation index in the round-cell portion. The sam e specific translocation t(12;16) and the fusion transcript type II in both components confirmed the close relationship between myxoid and round-cell liposarcomas. Telomerase activity and increased c-myc expression seem to be helpful molecular markers for characterizing tumor progression in myxoid l iposarcoma. Copyright (C) 1999 by W.B. Saunders Company.