A Case of Clear Cell Sarcoma-Like Tumor of the Gastrointestinal Tract (CCSLGT) with Two EWSR1-ATF1 Fusions

Clear cell sarcoma-like tumor of the gastrointestinal tract (CCSLGT) is an extremely rare mesenchymal tumor arising from the gastrointestinal tract. We report a case of CCSLGT with two fusion transcripts of EWSR1-ATF1. A 60-year-old female received ileectomy because of repeated ileus history. A 30-mm submucosal tumor with mucosal ulceration was detected in the ileum. Histologically, sarcomatous tumor comprised relatively monomorphic tumor cells arranged in sheets or nests and several multinucleated osteoclast-like giant cells. The main tumor cells contain small round nuclei with prominent nucleoli and abundant clear cytoplasm. Immunohistochemistry, the tumor cells expressed S-100 protein diffusely and focally expressed CAM5.2, EMA, and CD56. They did not express HMB-45, c-kit, CD34, desmin, and α-SMA. FISH analysis revealed EWSR1 split signal in the tumor cells. Reverse transcription polymerase chain reaction (RT-PCR) revealed 2 types of EWSR1-ATF1 transcripts, including EWSR1 exon 7-ATF1 exon 5 and EWSR1 exon 6-ATF1 exon 5. EWSR1-CREB1 was not detected. We finally diagnosed CCSLGT as well as identified two types of fusion transcript of EWSR1-ATF1.