Molecular confirmation of Ewing sarcoma

Objective: To analyze retrospectively results of reverse transcription poly merase chain reaction (RT-PCR) testing and demographic information in patie nts with known or suspected Ewing sarcoma/primitive neuroectodermal tumor f amily of tumors referred to the National Cancer Institute and to describe f actors influencing the determination of molecular marker status. Patients and Methods: Tumor samples from 76 patients from February 1997 to December 1999 were analyzed. In all cases, the diagnosis of this family of tumors was confirmed by histopathologic review. Results: In 58 patients, the presence of a translocation associated with th is family of turners was confirmed using RT-PCR. Specifically, there were 4 5 Ewing sarcoma (EWS)-FLI type 1 translocations, four EWS-FLI type 2 transl ocations, five EWS-ERG translocations, and four less common EWS-FLI variant s. Of patients with a confirmed translocation, four were confirmed only aft er nested RT-PCR techniques were used. In five patients who initially under went needle biopsy, the diagnosis was confirmed only after open biopsy or r epeat needle biopsy was undertaken. Samples from 18 patients were transloca tion-negative. Of these, seven samples were deemed inadequate for RT-PCR te sting as a result of inappropriate tissue handling or the presence of necro tic material. Five patients were found to have a different diagnosis after complete histopathologic and molecular characterization. Six samples remain ed, in which adequate tissue was obtained with no evidence of a characteris tic translocation. Conclusions: In apparently translocation-negative samples, close attention should be given to the possibility of an alternative diagnosis, the potenti al need for nested RT-PCR, and the possibility of an inadequate sample. Str ong consideration should be given to the use of open biopsy as opposed to n eedle biopsy to avoid the need for repeat biopsies and the potential for in accurate assessment of molecular marker status.