Frequent fusion of the JAZF1 and JJAZ1 genes in endometrial stromal tumors

Endometrial stromal tumors are divided into three types: benign stromal nod ules, endometrial stromal sarcomas, and undifferentiated endometrial sarcom as. A variety of cytogenetic abnormalities involving chromosome 7 have been reported in endometrial stromal sarcomas, including a recurrent t(7;17)(p1 5;q21). We have identified two zinc finger genes, which we have termed JAZF 1 and JJAZ1, at the sites of the 7p15 and 17q21 breakpoints. Analyses of tu mor RNA indicate that a JAZF1/JJAZ1 fusion is present in all types of endom etrial stromal tumors; however, the fusion appears to be rarer among endome trial stromal sarcomas that would be considered high-grade according to cer tain classification schemes. These findings suggest that the less malignant endometrial stromal tumors may evolve toward more malignant types, but tha t some endometrial stromal sarcomas with relatively abundant mitotic activi ty may compose a biologically distinct group.