OBJECTIVE: Uterine sarcomas are rare, lethal cancers, and little is known about their molecular etiology. The PTEN gene is located on chromosome 10q23.3, a region that displays frequent loss of heterozygosity in human uterine sarcomas. PTEN mutations have been described in 40% to 60% of uterine adenocarcinomas. To determine whether the PTEN gene is involved in the pathogenesis of uterine sarcoma, we analyzed deoxyribonucleic acid from uterine sarcomas and cell lines. STUDY DESIGN: Single-strand conformation analysis and direct sequencing of deoxyribonucleic acid were used to screen for PTEN mutations. RESULTS: Silent polymorphisms were detected in 2 of 36 primary uterine sarcomas. A 4-base pair deletion and a point mutation producing a stop codon were identified in 1 cell line. CONCLUSIONS: Mutational inactivation of PTEN does not play a major role in uterine sarcoma tumorigenesis, and another gene or genes on chromosome 10q may be implicated as a cause of these cancers. Differences in the molecular alterations underlying the development of uterine sarcomas and adenocarcinomas are significant.