Endometrial stromal sarcoma predominantly occurs as a primary tumor of the uterus. The most common cytogenetic abnormality in these tumors is t(7;17)(p15;q21), which occurs in 33% to 80% of cases and results in a JAZF1-JJAZ1 gene fusion. Rare cases of primary extrauterine endometrial stromal sarcoma have been reported, but it remains uncertain whether the genetic features of uterine endometrial stromal sarcoma are also characteristic of extrauterine tumors. The present study evaluates the prevalence of the t(7;17)(p15;q21) and JAZF1-JJAZ1 gene fusion in a series of 6 cases of primary extrauterine endometrial stromal sarcoma. Conventional nested reverse transcriptase-polymerase chain reaction was performed using primers complementary to sense and antisense JAZF1 and JJAZ1 sequences. Interphase fluorescence in situ hybridization was performed to detect t(7;17)(p15;q21) using a break-apart strategy for both JAZF1 and JJAZ1. In one of the 6 extrauterine endometrial stromal sarcoma cases, JAZF1-JJAZ1 fusion transcripts were detected by reverse transcriptase-polymerase chain reaction. The same case showed evidence of both JAZF1 and JJAZ1 rearrangements by interphase fluorescence in situ hybridization. The remaining 5 cases were negative for the t(7;17)(p15;q21) by both reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization analysis. These findings demonstrate that the t(7;17)(p15;q21) and associated JAZF1-JJAZ1 fusion transcripts are present in only a subset of primary extrauterine endometrial stromal sarcoma. Although molecular testing for the t(7;17)(p15;q21) and associated gene fusion may be useful for confirming primary extrauterine endometrial stromal sarcoma, the low prevalence of the genetic aberration limits the clinical utility of the testing.
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