Endometrial stromal sarcomas (ESS) represent <10% of all uterine sarcomas. 
Cytogenetic data on this tumor type are limited to 32 cases, and the karyotypes 
are often complex, but the pattern of rearrangement is nevertheless clearly 
nonrandom with particularly frequent involvement of chromosome arms 6p and 7p. 
Recently, a specific translocation t(7;17)(p15;q21) leading to the fusion of two 
zinc finger genes, juxtaposed with another zinc finger (JAZF1) and joined to 
JAZF1 (JJAZ1), was described in a subset of ESS. We present three ESS whose 
karyotypes were without the disease-specific t(7;17) but instead showed 
rearrangement of chromosomal band 6p21, twice as an unbalanced t(6p;7p) and once 
as a three-way 6;10;10 translocation. All three tumors showed specific 
rearrangement of the PHD finger protein 1 (PHF1) gene, located in chromosomal 
band 6p21. In the two tumors with t(6;7), PHF1 was recombined with the JAZF1 
gene from 7p15, leading to the formation of a JAZF1/PHF1 fusion gene. The third 
tumor showed a t(6p;10q;10p) as the sole karyotypic abnormality, leading to the 
fusion of PHF1 with another partner, the enhancer of polycomb (EPC1) gene from 
10p11; EPC1 has hitherto not been associated with neoplasia. The PHF1 gene 
encodes a protein with two zinc finger motifs whose involvement in tumorigenesis 
and/or tumor progression has not been reported before, but its rearrangement 
clearly defines a new pathogenetic subgroup of ESS.