Primary pelvic extraskeletal Ewing sarcoma: a case report and comprehensive literature review of molecularly confirmed cases arising within the female genital tract.

Introduction: Primary extraskeletal pelvic Ewing sarcoma within gynecologic organs is extremely rare and current literature is limited to case reports or series. Definitive diagnosis requires molecular confirmation of the EWSR1 fusion gene which drives cancer proliferation. Current treatment is guided by the National Comprehensive Cancer Network (NCCN) guidelines for Ewing sarcoma of the bone. Case Description: A previously healthy 21-year-old woman presented to her primary care provider with two weeks of malaise and pelvic symptoms. Imaging revealed a 10 cm heterogenous cystic and solid mass in the mid-pelvis appearing to arise from the anterior uterus with potential bladder invasion. She underwent exploratory laparotomy which included en bloc radical hysterectomy, bilateral salpingectomy, anterior vaginectomy, distal left ureterectomy, partial posterior cystectomy, and pelvic lymphadenectomy. Pathologic evaluation confirmed extraskeletal Ewing sarcoma through identification of an EWSR1 gene rearrangement. Margins were negative. The patient is undergoing adjuvant chemotherapy and PET scan 4.5 months postoperative showed no evidence of residual disease or metastasis.A comprehensive literature review identified 98 cases of molecularly-confirmed Ewing sarcoma occurring across gynecologic organs including the ovary, fallopian tube, broad ligament, uterine corpus, cervix, vagina, and vulva. Cases occurred in women across the lifespan. Treatment regimens and prognosis were variable. Conclusion: We present a unique case of primary pelvic extraskeletal Ewing sarcoma in a previously healthy young woman with localized invasion into the uterus, vagina, and bladder. Given the rarity of this disease, paucity of data, and potential for misdiagnosis, clinicians must maintain high suspicion for pelvic extraskeletal Ewing sarcoma.