Consistent Rearrangement of Chromosomal Band 6p21 with Generation of Fusion GenesJAZF1/PHF1andEPC1/PHF1in Endometrial Stromal Sarcoma

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.