Adult T-cell leukemia/lymphoma not associated with human T-cell leukemia virus type I

We describe five patients with adult T-cell leukemia/lymphoma (ATL) with neither integration of human T-cell leukemia virus type I (HTLV-I) into their leukemia cells nor anti-HTLV-I antibody in their sera. These findings indicate that HTLV-I may not have been involved in leukemogenesis in these patients. The clinicohematological, cytopathological, and immunological features of HTLV-I-negative ATL were exactly the same as those of HTLV-I-associated ATL. Leukemia cells with pleomorphic nuclei, generalized lymphadenopathy, hepatosplenomegaly, skin lesions, hypercalcemia, and elevated lactate dehydrogenase levels, all of which are characteristic features of typical ATL, were also seen in these patients with HTLV-I-negative ATL. Leukemia cells expressed T3, T4, and pan-T-cell antigens in three cases, and T3 and pan-T-cell antigens in two. All five patients had lived in ATL-nonendemic areas. The finding of HTLV-I-negative ATL suggests that factor(s) other than HTLV-I infection may be involved in ATL leukemogenesis.