LAUSR

Primary cutaneous extraskeletal Ewing sarcoma (EWS) is a primitive neuroectodermal tumor that usually occurs as a small, localized tumor on the trunk or extremities of young adults. The prognosis is typically reported to be quite favorable. It is extremely rare; only three cases of primary cutaneous EWS have been reported in Korea. In the first report, molecular genetic testing was not performed to make a definitive diagnosis. In the second report, reverse transcription polymerase chain reaction (RT-PCR) for EWS-FLI1 gene arrangement was done, but the result was negative. Although RT-PCR and fluorescence in situ hybridization (FISH) were performed in the third report, none of the results were shown in the article. Considering that genetic testing is an essential diagnostic tool for certain diseases, such as some brain tumors, we report a case of primary cutaneous extraskeletal EWS, including the result of RT-PCR. A 36-year-old Korean female presented with a cutaneous mass on the abdomen. Histological evaluation revealed solid sheets of primitive, small, uniform cells with hyperchromatic nuclei and scant cytoplasm. Immunohistochemistry stains were positive for CD99 and FLI1. RT-PCR showed a t(11;22) EWSR1 (Ewing sarcoma region 1)-FLI1 (Friend leukemia virus integration 1) translocation.