Activated killer cell lymphoma: an erythrophagocytic syndrome simulating histiocytic medullary histiocytosis

Histiocytic lesions involving the bone marrow

Histiocytic lesions involving the bone marrow include a number of reactive and neoplastic disorders. This article discusses the morphologic, immunophenotypic, and genotypic features of a variety of diseases associated with histiocytes and/or monocytes. Lysosomal storage disorders and hemophagocytic syndromes are often first diagnosed by bone marrow examination. Granulomas involving the bone marrow may also be the first indication of a systemic disorder. Apart from acute and chronic monocytic leukemias, the bone marrow is rarely involved by malignant histiocytic disorders, of which Langerhans cell histiocytosis is the most common.

Treatment strategies for Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH)

In Epstein-Barr virus (EBV) infection, the virus immortalizes B lymphocytes and cytotoxic T lymphocytes (CTLs) are directed toward both latent and lytic viral antigens expressed on EBV-infected B-cells. Various EBV-associated diseases occur as a result of this disruption of immune surveillance. In the majority of EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) cases, the major cell types containing EBV DNA are not B-cells, but clonally proliferating T-cells or NK-cells. Proliferation of these cells produces severe immune reactions in the host, and the clinical features related to massive cytokine production at the onset of disease are unique and distinct from other EBV-associated diseases. In the treatment of EBV-HLH, therapeutic infusion of EBV-specific CTLs appears to be ineffective, and eradication of EBV-containing cells is useful but not sufficient to save lives, because of high incidence of acute mortality due to cytokine-induced multiple organ failure and neutropenia-associated opportunistic infections. The optimal treatment strategy for this disease consists of three steps: (1) control of cytokine storm including coagulopathy and multiple organ failure, (2) control of opportunistic infections, and (3) eradication of clonally proliferating EBV-containing T- or NK- cells by immunochemotherapy and, if necessary, hemopoietic stem cell/bone marrow transplantation (SCT/BMT).

Angiotropic B-cell lymphoma with hemophagocytic syndrome

A unique autopsy case of angiotropic lymphoma, which is a rare lymphoma characterized by the lymphoma cells confined in blood vessels and with a minimal involvement of lymph nodes, is presented. The clinical diagnosis was a malignant histiocytosis (histiocytic medullary reticulosis), since clinical manifestations were muscle weakness of the extremities, pancytopenia, fever and hepatosplenonephromegaly, and biopsy exhibited infiltration by histiocytic cells showing hemophagocytosis in the liver sinusoids and the bone marrow, the latter with myelofibrosis. Postmortem examination revealed lymphoma cell proliferation within small blood vessels of the kidneys, perineural tissue of extremities and lungs. Lymph nodes were not involved. In the liver, spleen and bone marrow, prominent infiltration of benign histiocytic cells with active hemophagocytosis was evident but there was no lymphoma cell infiltration. No viral infection, including Epstein-Barr (EBV), was demonstrable either serologically or immunohistochemically. Autopsy diagnosis was angiotropic lymphoma of B-cell origin (immunophenotypically CD 45+, CD 20-related+, CD 45R+, CD 45 RO-, CD 43-, CD 57-, CD 30-, CD 68-) accompanied by hemophagocytic syndrome clinicopathologically simulating malignant histiocytosis.