Challenges in diagnosing an extraosseous Ewing sarcoma: A case report

•Extraosseous Ewing sarcoma (EES) is a highly malignant and rare tumour.•The diagnosis of EES sometimes is complicated and delayed.•EES though being a rare entity should be kept in the differential of retroperitoneal mass in children and adults.•High index suspicion of EES is advisable when dealing with patients with long lasting pain or haematoma without trauma, and other nonspecific symptoms followed by a palpable mass.•The treatment of EES should be multimodal. However, further studies in this area are needed to develop standardized EES treatment.