Hepatosinusoidal leukaemia/lymphoma consisting of Epstein-Barr virus-containing natural killer cell leukaemia/lymphoma and T-cell lymphoma; mimicking malignant histiocytosis.

Previously diagnosed cases of hepatosinusoidal T-cell lymphoma and malignant histiocytosis (MH) may include lymphoid neoplasms of natural killer (NK) cell lineage associated with Epstein-Barr virus (EBV). Such hepatosinusoidal neoplasms were found to demonstrate hepatomegaly but not lymphadenopathy, and all were diagnosed by a liver biopsy. Sixteen adult patients diagnosed with hepatosinusoidal leukaemia/lymphoma (six NK-cell leukaemia/lymphomas [NKLLs], five instances of MH, three T-cell malignant lymphomas [T-MLs], and two adult T-cell leukaemia/lymphomas [ATLLs] were examined for EBV by in situ hybridization, then were studied immunohistochemically and subjected to a DNA analysis. Among our five patients with MH, neoplastic cells showed T-cells, but no histiocytic markers, and they were considered to have either a T-cell or NK-cell lineage. All NKLLs, MHs and T-MLs, except for ATLLs accompanied by reactive hemophagocytic histiocytes, varied in number in each case. In situ hybridization revealed the presence of EBV in the nuclei of atypical cells in all of the six lymphoid neoplasms of NK-cell lineage. Each case of MH and each T-ML which represented EBV demonstrated no definite T-cell or histiocytic markers. Patients with ATLL did not reveal EBV. In all patients with hemophagocytosis, EBV was present in the nuclei of the neoplastic lymphocytes, but not in the hemophagocytic cells. Finally, the 16 cases were reclassified into eight cases with EBV-containing NKLLs, six T-MLs, and two ATLLs. In addition, no true histiocytic neoplasms were observed. The mechanism of hemophagocytosis may be therefore the production of lymphokines (macrophage-activating factors) by neoplastic lymphocytes. EBV-associated hepatosinusoidal leukaemia/lymphoma may thus contain a lymphoid neoplasm of NK-cell lineage, which made it difficult to be distinguished from the previously designated malignant histiocytosis.