MALIGNANT HISTIOCYTOSIS-LIKE B-CELL LYMPHOMA, A DISTINCT PATHOLOGICALVARIANT OF INTRAVASCULAR LYMPHOMATOSIS - A REPORT OF 5 CASES AND REVIEW OF THE LITERATURE

Malignant histiocytosis (MH)-like B-cell lymphoma (BCL) is a neoplasti c proliferation of large B cells clinically characterized by fever, he patosplenomegaly, haemophagocytosis and abnormal laboratory data, with out lymphadenopathy or skin lesions. Interestingly, most cases have be en reported in Asian patients, and it is unclear whether MH-like BCL i s biologically distinct from conventional large B-cell lymphomas, Mie report five Japanese patients with MH-like BCL. Biopsied specimens of bone marrow, liver and/or spleen showed infiltration of neoplastic B c ells accompanied by haemophagocytosing histiocytes. Lymphoma cells wer e positive for CD19, CD20 and HLA-DR surface antigens, and negative fo r CD5 and CD10. In four cases elevated serum levels of interleukin (IL )-6 and the soluble IL-2 receptor isoform were noted, but not IL-1 bet a, IL-2 or tumour necrosis factor-alpha, Autopsies of two cases were p athologically diagnosed as intravascular lymphomatosis (IVL). Based on these observations, the current and nine previous cases reported as M H-like BCL in Japan were re-evaluated. They appear to form a peculiar variant of IVL, characterized by bone marrow involvement at presentati on, haemophagocytic syndrome, and a rapidly aggressive clinical course , but rarely neurological complications or skin lesions. This variant may merit separate consideration because of the problems posed in the initial diagnosis and therapeutic approaches.