Clear Cell Odontogenic Carcinoma: Occurrence of EWSR1-CREB1 as Alternative Fusion Gene to EWSR1-ATF1.

Clear cell odontogenic carcinoma (CCOC) is a rare, low-grade malignant epithelial neoplasm, occurring in the jawbones, mainly affecting the mandible of elderly patients. In addition to hyalinizing clear cell carcinoma of the salivary gland, it is one of the epithelial neoplasms known to harbor an EWSR1-ATF1 fusion. Therefore, a link between these tumors seems plausible. We describe six cases of CCOC showing EWSR1 rearrangements, with two cases being positive for the ATF1 partner gene using FISH analysis. In one case, an EWSR1-CREB1 fusion was identified using RT-PCR, which we report for the first time in this tumor type. The other three cases investigated by FISH were negative for ATF1, CREB1 and CREB3L2. In conclusion, our data show that EWSR1-CREB1 is an alternative fusion gene to EWSR1-ATF1 in CCOC.