Case Report Cytogenetic Confirmation of a Gastrointestinal Stromal Tumor and Ewing Sarcoma/Primitive Neuroectodermal Tumor in a Single Patient

We report a rare case in which two tumor entities, a gastrointestinal stromal tumor (GIST) and Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET), with distinct cytogenetic features occurred in a single patient. The patient was a 72-year-old woman. The first tumor was a sub-mucosal gastric tumor and was diagnosed as a low-risk group GIST based on morphological characteristics and the results of an immunohistochemical analysis for c-kit and CD34. Further cytogenetic analysis revealed that this tumor had a pointmutation (D842V substitution) in exon 18 of the platelet-derived growth factor receptor alpha gene. The second tumor was foundmore than 4 years after the appearance of the first tumor. ES/PNETwas highly suspected both morpholog-ically and immunohistochemically, and the diagnosis was confirmed by the detection of an EWS rearrangement using a fluorescence in situ hybridization technique. Although the cyto-genetic correlations of these two tumors are unclear, accurate histologic recognition is of clinical importance because the treatments for these two tumors differ. Key words: gastrointestinal stromal tumor (GIST) – Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) – KIT/c-kit – platelet-derived growth factor alpha (PDGFRA