The tumor suppressor gene PTEN/MMAC1 was identified on chromosome 10q23.3, which is homozygously deleted in many human malignancies. The loss of chromosome 10q was also frequently reported in some types of soft tissue sarcomas. Our study was designed to investigate the frequency of PTEN/MMAC1 gene mutation and to evaluate the role of the PTEN/MMAC1 gene in the tumorigenesis of soft tissue sarcomas without specific balanced translocations. We analyzed 51 cases of soft tissue sarcomas without specific balanced translocations for PTEN/MMAC1 mutations by polymerase chain reaction-single strand conformation polymorphism and direct sequencing. Mutations in the PTEN/MMAC1 gene were found in only 2 cases (3.9%). Both tumors with PTEN/MMAC1 mutation were leiomyosarcomas arising from the retroperitoneum and inferior vena cava, respectively. Two of 3 leiomyosarcomas arising from the intra-abdominal cavity examined harbored mutations of this tumor suppressor gene. This result suggests that leiomyosarcomas derived from the intra-abdominal cavity might have different tumorigenesis from those of an extremity or the trunk, from the viewpoint of PTEN/MMAC1 mutation, although PTEN/MMAC1 gene mutations are rare event in these soft tissue sarcomas.
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