Pathology of soft-tissue tumors: daily diagnosis, molecular cytogenetics and experimental approach

This article reviews problems in diagnostic pathology and molecular cytogenetics of soft-tissue tumors. Also discussed are the origin of soft-tissue sarcomas and the molecular basis of effective target therapy for sarcomas. Molecular cytogenetic analysis of tumor-specific chromosomal translocations and associated fusion gene transcripts offers a useful adjunct to the diagnosis of soft-tissue tumors, but recent studies have indicated a growing number of fusion gene variations in each tumor type. In pleomorphic sarcoma/malignant fibrous histiocytoma, the alternative lengthening of telomeres (ALT) mechanism may result in formation of anaphase bridges and marked nuclear pleomorphism. The histogenesis of soft-tissue sarcomas has been a matter of controversy. In the present experimental model using s.c. injection of 3-methylcholanthrene in C57BL/6 mice pretreated with bone marrow-transplantation from green fluorescent protein (GFP)-positive green mice, the bone marrow-derived mesenchymal stem cells as well as the tissue-resident mesenchymal cells in the peripheral soft tissues are possible originators of sarcomagenesis. Little is known about a molecular basis of target therapy for sarcomas. Platelet-derived growth factor-BB (PDGF-BB) enhances the invasive activity of malignant peripheral nerve sheath tumor (MPNST) cells through platelet-derived growth factor receptor (PDGFR) phosphorylation, whereas imatinib mesylate inhibited such activity, suggesting that targeting PDGFR-beta may result in the establishment of novel treatment for MPNST. In addition, emmprin is a transmembrane glycoprotein on tumor cells that stimulates peritumoral fibroblasts to produce matrix metalloproteinases (MMP), playing a crucial role in tumor progression, invasion and metastasis. The MMP upregulation mechanism mediated by tumor-associated emmprin may be a potentially useful target in anti-tumor invasion therapy for sarcomas.