PA23 Primary cutaneous Ewing sarcoma in a 14-year-old boy

Abstract

A 14-year-old boy presented with a 7-month history of a nodule on the right shoulder. It was initially pink and pea-sized but developed black areas as it grew. It was nontender but bled occasionally. He was otherwise well and took no regular medications. He was originally from the Philippines, having moved to the UK 2 years previously. His mother had a history of breast cancer. This was suspected to be a pyogenic granuloma and treated with a shave biopsy. Histology showed largely patternless sheets of small, blue, round cells, with diffuse and strong membranous reactivity for CD99 on immunohistochemistry. Further molecular analysis revealed EWSR1–FLI1 fusion, confirming Ewing sarcoma. Staging imaging showed no metastatic disease. Following further surgery, he was treated as per the Euro-Ewing protocol with vincristine (V), doxorubicin (D), cyclophosphamide (C), ifosfamide (I), etoposide (E; nine induction cycles: alternate VDC/IE followed by five consolidation cycles IE/VC). Ewing sarcoma most commonly arises from bone and is the second most common bone malignancy in children with an incidence of 2.93 per million. Primary cutaneous Ewing sarcoma is extremely rare, with most of the literature consisting of case reports. A 2015 retrospective review of 56 cases of cutaneous/subcutaneous Ewing sarcoma from the UK and France found that most cases were on the extremities (48%) or trunk (39%). Primary cutaneous Ewing sarcoma tends to occur in late-adolescent or young-adult females, whereas bone disease affects younger patients with a male predominance. Current treatment is similar to treatment for Ewing arising from bone. However, primary cutaneous Ewing sarcoma has a more favourable prognosis, with a 5-year overall survival rate of 93.8%. In summary, cutaneous Ewing sarcoma is a very rare malignancy, particularly in the paediatric population. It is important to consider this in the differential diagnosis of erythematous nodular lesions in children, in order to minimize delays in treatment.