All of the members of the peripheral primitive neuroectodermal tumor family (Ewing sarcomas, neuroectodermal tumors of bone, peripheral neuroepitheliomas, and Askin tumors) have similar morphologic and immunophenotypical features (ie, the proliferation of small and medium-sized round cells in a fibrous background showing strong and diffuse immunohistochemical positivity for CD99), and the common cytogenetic abnormality of a nonrandom translocation involving the EWS gene and one of several members of the erythroblastosis virus transforming sequence family of transcription factors. The combination of clinical information and morphologic/immunophenotypical characteristics is usually sufficient for a correct diagnosis, but there are rare cases in which an unusual predominant or multidirectional immunophenotypical differentiation makes diagnosis a challenge and requires the use of molecular cytogenetic or molecular techniques. We describe 3 such cases in which we employed fluorescence in-situ hybridization analysis to detect translocation involving the EWS gene and reverse transcription polymerase chain reaction followed by sequencing to detect the fusion transcript EWS-FLI1.
Anatomic Pathology B Unit, Department of Pathology
† Experimental Molecular Pathology Unit, Department of Pathology
§ Adult Sarcoma Medical Oncology Unit, IRCCS Istituto Nazionale Tumori of Milan, Milan
‡ Department of Pathology, Piacenza Civil Hospital, Piacenza, Italy
This work was supported by grants from Associazione Italiana per la Ricerca sul Cancro (AIRC).
Correspondence: Marta Barisella, MD, Department of Pathology, Anatomic Pathology B Unit, IRCCS Istituto Nazionale Tumori of Milan, 20133 Milano, Italy (e-mail: firstname.lastname@example.org).