Microsatellite alterations in various sarcomas in Japanese patients

To determine the usefulness of microsatellite analysis in the differential diagnosis of various sarcomas, we investigated microsatellite alterations at 12 microsatellite loci by polymerase chain reaction and electrophoresis in 39 Japanese patients with sarcomas. The sarcomas were: osteosarcoma, Ewing's sarcoma, chondrosarcoma, liposarcoma, leiomyosarcoma, epithelioid leiomyosarcoma, rhabdomyosarcoma, synovial sarcoma, and malignant fibrous histiocytoma. We also examined ten leiomyomas to contrast with leiomyosarcoma. No microsatellite instability (MSI) or loss of heterozygosity (LOH) were found in Ewing's sarcoma, chondrosarcoma, epithelioid leiomyosarcoma, malignant fibrous histiocytoma, and leiomyoma. Only three patients, one each with liposarcoma, leiomyosarcoma, and synovial sarcoma, manifested MSI, whereas, osteosarcoma, liposarcoma, leiomyosarcoma, rhabdomyosarcoma, and synovial sarcoma manifested LOH, with an incidence of 43%, 14%, 86%, 20%, and 75%, respectively. Interestingly, three patients showed unusual patterns of LOH, probably due to intratumoral heterogeneity. Kaplan-Meier analysis revealed that LOH on 11p was predictive of poor prognosis in osteosarcoma. The low incidence of MSI indicates that MSI is not necessary for neoplastic transformation in sarcomas. However, the very high incidence of LOH in leiomyosarcoma indicates that microsatellite analysis may serve for the differential diagnosis of leiomyosarcoma versus leiomyoma. Microsatellite analysis may also predict prognosis in osteosarcoma.