Follicular lymphoma presenting as hyperleucocytosis.

Follicular lymphoma is the second most common subtype of non-Hodgkin's lymphoma affecting adults. Clinically, follicular lymphoma is generally indolent, most often presenting as a painless peripheral lymphadenopathy; however, a leucocytosis at presentation is exceedingly rare. We present the case of a 63-year-old woman with follicular lymphoma with a presenting hyperleucocytosis at diagnosis of 1 327 000/μL demonstrated on laboratory analysis work while hospitalised for progressive weakness. fluorescence in situ hybridization (FISH) panel was consistent with follicular lymphoma, which was positive for B-cell leukaemia/lymphoma 2 and negative for MYC Proto-Oncogene. Cytoreduction with rituximab-containing therapy was initiated, with the patient ultimately expiring. A leukaemic phase at presentation appears to be associated with poor outcome. The findings from our case, in addition to others, have potential implications in regard to prognostic utility. The current prognostic tool used to estimate overall survival for follicular lymphoma, Follicular Lymphoma International Prognostic Index, does not take leucocytosis into account. © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.