Central nervous system involvement in indolent lymphomas

Background: Central nervous system (CNS) involvement, a well-recognized complication of aggressive non-Hodgkin's lymphomas (NHL), has rarely been reported in indolent lymphomas. Large series have reported this complication in 3% of indolent NHLs, generally following histological transformation. Patients and methods: We retrospectively reviewed the disease characteristics and clinical course in seven patients (six females, one male) with indolent B-cell lymphomas who developed CNS involvement during various stages of their illness. Results: The median ages at diagnosis of systemic and CNS lymphoma were 60 and 63 years, respectively. Histologies were: small lymphocytic lymphoma (two), follicular lymphoma grade I (two), follicular lymphoma grade II (two) and unclear low-grade histology (one). There were diverse neurological symptoms. Two patients had parenchymal involvement, three had leptomeningial involvement and two had both. Systemic lymphoma was found in all patients, all but one having bone marrow involvement. Four patients had a transformation to high-grade histology. Six patients were treated with systemic and intra-cerebrospinal fluid chemotherapy, and two received radiotherapy as well. Five patients achieved CNS response. Survival was 1-9 years for treated patients (median 2 years). Three patients died of CNS disease. Conclusions: CNS involvement is a rare and unexpected complication of indolent NHL, which should be considered in the differential diagnosis of patients presenting with new neurological signs. This condition is treatable and some patients have a long clinical course.