Aleukemic granulocytic sarcoma with AML1/ETO fusion gene expression and clonal T cell populations

We report a unique case of aleukemic granulocytic sarcoma of the neck, orig inally misdiagnosed as non-Hodgkin's lymphoma (NHL), though chloroma was al so suspected due to a greenish macroscopic appearance and the presence of m yeloid chloroacetate esterase (CAE) + cells. The proof of clonal T cell rec eptor gamma chain (TeR gamma) gene rearrangements in the recurring tumor wa s deemed to confirm the initial diagnosis of T cell NHL. Altogether five di stinct types of clonal TcR gamma gene rearrangements were found in the tumo r, bone marrow and peripheral blood. Only retrospectively, using RT-PCR, di d we detect the acute myeloid leukemia subset-specific fusion gene AML1/ETO in the frozen samples of the relapsed tumor, as well as in the otherwise u naffected bone marrow and peripheral blood (representing 'minimal initial d isease' in the latter two samples). Simultaneous staining verified that the neoplastic CAE + cells and CD45RO + T cells were different populations. (C ) 2001 Elsevier Science Ltd. All rights reserved.