47. Primary cutaneous Ewing's sarcoma

Abstract

The Ewing's sarcoma breakpoint region 1 gene ( EWSR1, chromosome 22q12) is ubiquitously expressed in human cells but the function of its encoded protein has not yet been elucidated. Rearrangements involving EWSR1 were first described in Ewing sarcoma/peripheral neuroectodermal tumours (PNET) and are now seen in a variety of soft tissue tumours. Most Ewing's sarcoma cases involve fusion with FLI1 , with a minority involving ERG and rarely ETV1 , ETV4 and FEV genes amongst others. Cutaneous primary presentation of Ewing's sarcoma is rare and most cases possess the classic FLI1 t(11;22). Careful clinical and histological examination is required to exclude both a deep-seated primary malignancy and the differential list of small round blue cell tumours. We present a case of primary cutaneous Ewing's sarcoma arising as nodule in the left upper back of a 14 year old male. Histological and immunohistochemical features were highly suggestive of a Ewing's sarcoma/PNET. Fluorescence in-situ hybridisation showed a EWSR1 gene rearrangement confirming the tumour belonged to the Ewing's sarcoma family. However the translocation did not involve the common FLI1 or ERG translocation partners, implying possession of the rarer translocation partners which are not routinely assayed in our local diagnostic laboratory. The patient went on to have post-resection chemotherapy and follow up radiology ten months later showed absence of recurrent or metastatic disease.