Embryonal rhabdomyosarcoma (ERS) is an extremely rare neoplasm accounting for approximately 10% of all pediatric sarcomas. It is primarily seen arising from the cervix (37.5%) or vagina (32.6%) and less likely the uterus (12.5%). An adolescent female presented with abnormal uterine bleeding (AUB) thought to be ovulatory in origin, but unfortunately the diagnosis was more sinister. We present a case of uterine ERS. Although the diagnosis is rare, this case serves as a reminder to keep a wide differential and not forget the zebras.

The patient is a 16 year-old African American female with a medical history significant for AUB and obesity that presented after feeling pelvic pressure. While performing Valsalva to relieve the pressure, she subsequently had a mass prolapse through her vagina. Her exam was significant for a necrotic mass protruding past the introitus with portions appearing like grape-like clusters (Figure 2). She had two previous visits for symptomatic anemia requiring transfusions and IV estrogen, followed by an oral hormone taper. Her bleeding improved, but when her taper decreased to two pills a day, her vaginal bleeding increased again. She had ultrasound with the first presentation that was read as “blood products within the endometrial canal and proximal vagina” (Figure 1). She had a local debulking at this presentation and final pathology revealed ERS. She underwent neoadjuvant chemotherapy and gross total resection with a laparoscopic hysterectomy and bilateral salpingectomy. Pathology confirmed Stage I. Due to amputation of the uterus within the vaginal canal at time of gross resection, radiation is being considered.

ERS is a rare neoplasm accounting for approximately 10% of all pediatric sarcomas and typically appears between ages 10-22. A typical ultrasound description of uterine ERS is solid appearing with heterogenous echogenicity and often vascular. Management is often a combination of surgery, hysterectomy with ovarian preservation, followed by chemotherapy, a combination of Vincristine, dactinomycin, and cyclophosphamide. 5-year survival for the patient's age group is 82%. Radiation is reserved for more advanced cases typically. The greatest prognostic factor for these patients is staging at time of diagnosis. This patient exhibited the symptoms of ERS at inital presentation; however, her profound anemia and imaging read lead providers down a more common pathway. In hindsight, the clinical course of recurrent episodes of AUB warranted further investigation. While it is important to remember that common things are common, it is also crucial to keep a wide differential and remember that zebras have hooves too.