HTLV-1 unrelated adult T-cell leukemia/lymphoma with unique phenotype and karyotype

We describe a unique case of adult T-cell leukemia/lymphoma (ATL). The patient had typical clinicohematological features as ATL, but showed a lack of antibody to human T-cell leukemia virus type-1 (HTLV-1) and was negative for HTLV-1 proviral DNA in the peripheral mononuclear cells by means of polymerase chain reaction. The phenotype of tumor cells revealed CD7+, CD5+, CD2+, CD3+, WT31-, TcR delta 1-, CD4-, CD8-, CD25-, and the karyotype showed a 5q-, t(12;18). HTLV-1 unrelated ATL is very rare, and the karyotype as in our case has not been reported previously.