EWING TUMOR AFTER TREATMENT OF KI-1(-CELL LYMPHOMA - THERAPY-ASSOCIATED SECONDARY NEOPLASM OR UNRELATED COINCIDENCE() ANAPLASTIC LARGE)

We report on a 20-year-old woman who developed a pelvic small round ce ll tumor with lung metastases 8 years after diagnosis and successful t reatment for Ki-1-positive anaplastic large cell lymphoma (Ki-1(+) ALC L) with histiocytic differentiation. Molecular genetic detection of EW S/FLI-1 fusion gene expression in the second tumor by RT-PCR unambiguo usly confirmed the histopathologic diagnosis of Ewing tumor (ET), wher eas no evidence for the presence of this specific gene rearrangement w as obtained in a retrospective analysis of the lymphoma tissue. In con trast, expression of a NPM/ALK chimeric gene was observed which was ab sent in the ET Moreover, the lymphoma contained a monoallelic D delta 2-D delta 3 T-cell receptor gene rearrangement which was also absent i n the ET. Thus, our histopathologic, immunohistochemical, and, in part icular, molecular genetic studies support the notion that these tumors were most probably pathogenetically unrelated. Since this is the firs t report describing such an association between a non-Hodgkin's lympho ma and ET and, since the latter has only rarely been observed as a sec ond malignant neoplasm, it remains a matter of speculation whether in this patient ET developed as a therapy-related secondary neoplasm or i ndependently from the lymphoma as a consequence of either genetic tumo r predisposition or mere accidental coincidence.