An Asian variant of intravascular lymphomatosis: an updated review of malignant histiocytosis-like B-cell lymphoma.

Malignant histiocytosis-like B-cell lymphoma (MH-like BCL) is characterized clinically by hemophagocytic syndrome (HPS), bone marrow involvement at presentation, and an aggressive clinical course. Yet, it remains an ill-defined disease entity. We recently described five cases of MH-like BCL and suggested that these may be regarded as a peculiar variant of intravascular lymphomatosis (IVL), based on clinical and pathological observation. Interestingly, this type of lymphoma has been reported exclusively among Asians, with few reports from Western countries, and therefore we propose that this variant be noted as an Asian variant of IVL(AIVL). To evaluate the incidence of this variant, we performed a literature search for English or Japanese studies dealing with MH-like BCL or B-cell IVL associated with HPS (IVL with HPS). We found 18 reports of MH-like BCL and 16 reports of IVL with HPS and re-evaluated the clinicopathologic aspects of each study with respect to AIVL. Although several differences were noted, such as gender, presence of respiratory changes, bone marrow invasion and disseminated intravascular coagulopathy, there were also overlapping profiles and they appeared to be consistent with the AIVL single disease entity. Of particular note was the absence of peripheral lymphadenopathy and tumor formation which posed diagnostic problems in the initial phase of the presentations. Thus, based on analysis of the clinical findings of these 34 cases, the diagnostic criteria for AIVL consists primarily of cytopenia (anemia and/or thrombocytopenia), hepatosplenomegaly, absence of peripheral lymphadenopathy and tumor formation, and erythrocyte-hemophagocytosis along with intravascular proliferation of the neoplastic B cells. The pathologic findings of the 19 autopsied cases which fulfilled the criteria are also summarized, and they reveal morphologic, immunologic, and genotypic features of typical IVL.