Retroperitoneal Ewing's sarcoma/embryonal tumor: a rare differential diagnosis of back pain

摘要

A previous healthy 17-year-old female was referred to a rheumatology clinic due to a 6-month history of lower back pain. Her pain worsened at night and did not radiate. During that 6-month period, she had lost weight (5 kg). An initial evalu- ation produced normal cardiovascular and abdominal find- ings. She had pain on lumbar spine palpation and pain when her sacroiliac joints were examined (Patrick's test). Laboratory tests showed normal blood smear results and normal levels of inflammatory markers. While waiting for a magnetic resonance imaging (MRI) scan of her sacroiliac joint, she returned with significant worsening of her pain and weakness in her right leg. Examination showed grade 3 muscle strength and an absence of the ipsilateral patellar reflex. MRI revealed a right paraverte- bral mass, with intradural and foraminal components, showing a signal that was, in comparison with the muscle signal, pre- dominantly isointense (with a hyperintense component indicat- ing hemorrhage) on T1-weighted images and isointense (with a hyperintense necrotic component) on T2-weighted images (Fig- ure 1). Ultrasound-guided biopsy revealed an undifferentiated small round-cell morphology. Immunohistochemistry staining suggested a member of the Ewing's sarcoma/embryonal tumor (ES/ET) family (Figure 2). The patient was submitted to chemo- therapy, which did not elicit an adequate response.