Intravascular lymphoma (IVL) is a rare type of extranodal lymphoma in which the lymphoma cells proliferate exclusively in lumina of small vessels. Here, we report a clinicopathological study of 13 cases IVL diagnosed at our institution between March 1999 and July 2007, and evaluated the clinical characteristics, usefulness of random skin biopsy and response to chemotherapy containing rituximab. Three of 13 patients were diagnosed at autopsy. The most common clinical features were unexplained fever, neurological deterioration, respiratory failure, and poor performance status. Thrombocytopenia, high serum lactate dehydrogenase and soluble interleukin2 receptor levels were the most common laboratory abnormalities. Adrenal tumor was detected in four cases and pituitary involvement was seen in all three autopsied cases and in two surviving patient by brain magnetic resonance imaging. Bone marrow invasion was seen in all 13 cases by bone marrow smear, and it was subtle in trephine biopsy. Immunohistochemical analyses revealed that CD5 was positive in one-third of the cases. Most of the cases were positive for MUM1/IRF, Bcl-2 and negative for CD10 and BCL-6 indicating the postgerminal center cell origin of this peculiar type of lymphoma. On random skin biopsy, the most recent seven patients were diagnosed promptly and chemotherapy containing rituximab was successfully administered. Patients with IVL exhibit the characteristic clinical and immunophenotypic features cited above and the use of random skin biopsy facilitates prompt diagnosis. Early commencement of chemotherapy containing rituximab appears promising for this peculiar lymphoma. As the recent seven patients were diagnosed by random skin biopsy over the past 13 months, the incidence of IVL is thought to be much higher than generally accepted.
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