Hyperleukocytosis in Metastatic Solid Tumors, A Benign Paraneoplastic Syndrome of Poor Prognosis: Short Review of Literature

Leukemoid reaction describes an important leukocytosis (more than 50,000 white blood cells/mm3) with increased early neutrophil precursors. It is secondary to a physiologic stimulation of the bone marrow in most of the cases. It is called paraneoplastic when it is the consequence of cytokine storm induced by malignant processes. Many solid tumors have been associated with paraneoplastic leukocytosis in the literature. The elevated white blood cells (WBC) count is a benign process by itself, but it is associated with bad prognosis and dramatic evolution of the underlying neoplasms. After reviewing the literature concerning the Paraneoplastic Leukemoid Reaction (PLR), case reports and small case series, I am writing a small review in order to increase the clinicians’ awareness about this rare but serious condition. It is considered an indirect marker of poor outcome.