Leptomeningeal involvement by relapsed follicular lymphoma detected by flow cytometry despite exceedingly low white blood cell counts in cerebrospinal fluid: A case report

Follicular lymphoma is usually an indolent non-Hodgkin lymphoma that rarely involves the central nervous system (CNS) and flow cytometric detection of such lymphoma in cerebrospinal fluid (CSF) is often challenging because of low cellularity and viability of CSF samples. Here, we report our experience in a 52-year-old man whose relapsed follicular lymphoma with leptomeningeal involvement was confirmed by flow cytometric analysis of CSF, despite an exceedingly low white blood cell count (3/cumm).