Intravascular large B-cell lymphoma presenting with mass lesions in the central nervous system: a report of five cases.

We have encountered five cases of intravascular large B-cell lymphoma (IVL) presenting with central nervous system (CNS) mass lesions during their clinical course. The age of the patients ranged from 50 to 74 years and three patients were male. All of these cases histopathologically showed typical intravascular localization of the neoplastic cells in the initial biopsy specimens obtained from sites other than the CNS. Despite multiagent chemotherapy, patients suffered from single or multiple CNS mass lesions 5-44 months after the initial diagnosis of IVL, except for one case in which IVL and the CNS mass lesion were diagnosed at the same time. The subsequent biopsy and autopsy specimens obtained from the CNS mass lesions revealed diffuse infiltration of the tumor cells with perivascular spreading, but minimal or no intravascular components. Immunohistochemical analysis of intravascular tumor cells and CNS mass lesions revealed expression of CD20, CD79a, bcl-2 and negative for CD3e and Epstein-Barr virus encoded RNA. The overall features of the CNS mass lesions were very similar to or indistinguishable from those of the primary CNS lymphomas. This implies that CNS mass lesions in the IVL cases can be correctly diagnosed only by careful attention to clinical and pathological findings. Moreover, there is the possibility that some cases previously diagnosed as primary CNS lymphomas may have include IVL cases. Further investigation is needed to explore this unusual phenomenon.