Peripheral Neuroectodermal Tumors

Abstract

James Ewing described Ewing sarcoma in 1921 as an “endothelioma of bone” (1). He believed at the time that it arose from the osseous blood vessels and later realized that the tumor was more complex, describing it as an “endothelial myeloma” (2). Ewing is credited with differentiating this tumor from neuroblastoma and lymphoma. In 1979, Askin and Rosai described a “malignant small cell tumor of the thoracopulmonary region” in 20 children and adolescents with a median age of 14.5 years and with a female rather than male predominance, as seen in Ewing sarcoma of bone (3). These authors noted a predilection for local recurrence. In the present era, most texts refer to the Ewing sarcoma family of tumors that include not only the highly malignant small round cell tumors of bone originally described by Ewing but also the chest wall tumors described by Askin, as well as extra-skeletal Ewing sarcoma, and peripheral primitive neuroectodermal tumors (PNET) (peripheral neuroepithelioma). A unifying feature of these tumors is the presence of a reciprocal translocation between chromosomes 11 and 22 (t11;22)(q24;q12) in approximately 85%. This is considered pathognomonic superseding other forms of pathologic analysis, like immunohistochemistry (4). Of great practical importance is that the surgeon must assure that an adequate amount of biopsy tissue is preserved fresh and sterile so that molecular genetic analysis can confirm the diagnosis. This chapter describes the diagnosis, treatment, reconstructive procedures, and late-treatment sequelae of PNET of the chest wall (Askin’s tumor, chest wall Ewing sarcoma). These chest wall tumors comprise 16% of all Ewing sarcomas, with most arising from ribs (63%), followed by scapula (25%), clavicle (9%), and sternum (3%) (5). Ewing sarcoma family of tumors generally metastasize to lung (10%) and bone (10%), or combinations of the two (6%). The rate of metastases for chest wall primary tumors is lower, and was commented upon in the initial paper by Askin (3).