Ganglioneuronal Differentiation in Ewings Sarcoma of the Chest Wall (Askin Tumour): An Uncommon Post-Chemotherapy Change

Abstract

Ewing sarcoma is classified under undifferentiated small round cell sarcomas of bone and soft tissue. Such tumours arising in the chest wall were previously called Askin’s tumour, however this terminology is not preferred at present. These tumours classically have a small round cell morphology and fusion of FET family of genes (usually EWSR1) with a member of the ETS family of transcription factors. Rare cases of Ewing sarcoma are found to have extensive neural differentiation with ganglion cells and neuropil at diagnosis as well as following chemotherapy. We report a 12 year old boy who presented with a large mass in the right hemi-thorax, which was diagnosed as Ewing sarcoma with EWSR1 translocation by FISH. However, following four cycles of chemotherapy (Vincristine, Doxorubicin, Cyclophosphamide alternating with ifosphamide and etoposide), the resection specimen showed predominantly neural differentiation mimicking a ganglioneuroma with only small areas of small round cell component. EWSR1 translocation was also demonstrated in the resection specimen. After a period of nine months, the child presented with recurrence at the same site and was treated with Irinotecan, cyclophosphamide with topotecan and temozolamide giving excellent clinical response. In this paper, we emphasize the rare occurrence of extensive neural differentiation in Ewing sarcoma and the need to revisit the upfront chemotherapy protocols for patients who exhibit this rare phenomenon