A rare case report and literature review of Ewing sarcoma of the vagina

Abstract

Primary Ewing sarcoma of the vagina is rare. Here we report the only case in a large tertiary center in the past 20 years. A 47-year-old female with vaginal bleeding had imaging revealing a mass in the upper vagina extending into the lower uterine segment and urethra. Outside biopsies demonstrated a high-grade small round blue cell tumor, with focal immunoreactivity for cytokeratin AE1/3, CAM5.2, PAX8, synaptophysin and chromogranin. An initial diagnosis of high-grade carcinoma with focal neuroendocrine differentiation was made, and the patient had partial response to chemoradiation. Subsequent TEMPUS genomic testing revealed EWSR1-FLI1 somatic gene fusion, suggesting Ewing sarcoma. CD99 immunohistochemistry (IHC) was performed and showed diffuse membranous staining. A diagnosis of Ewing sarcoma of the vagina was rendered. Primary Ewing sarcoma should be included in the differential diagnosis of a high-grade small round cell tumor of the vagina as it may show variable IHC pattern, mimicking Müllerian or neuroendocrine carcinoma. CD99 and Fli-1 IHCs are helpful to point to this diagnosis, and molecular analysis with the characteristic EWSR1 gene fusion confirms it. The prognosis of Ewing sarcoma of the vagina is like that in other sites, and more favorable than those in typical locations.