Esophageal extraskeletal Ewing's sarcoma.

Extraskeletal Ewing's sarcoma is a rare tumor. The most common sites of occurrence are on the trunk, extremities, and retroperitoneum. This type of tumor is well characterized by recurrent chromosomal translocation such as t (11;22) (q24;q12) (EWSR1/FLI1) or t (21;22) (q22;q12) (EWSR1/ERG) and overexpression of MIC2/CD99 on tumor cell membrane. We describe the first reported case of an esophageal extraskeletal Ewing's sarcoma with confirmation from immunohistochemical and molecular diagnoses. A 56-year-old man developed a polypoid tumor located in the lower part of the esophagus. The tumor was composed of small-sized round cells showing prominent fibrillar cytoplasmic processes. Intracytoplasmic glycogen was detected in all the tumor cells. Immunoreactivity for MIC2/CD99 was positive on the membrane of all tumor cells. A reverse transcriptase-polymerase chain reaction followed by sequencing revealed an EWSR1/ERG chimeric transcript, which combined EWSR1 exon 10 with ERG exon 6. The present report added a new entity of esophageal small round cell tumor.