Non‐small‐cell lung cancer associated with excessive eosinophilia and secretion of interleukin‐5 as a paraneoplastic syndrome

Abstract Eosinophilia associated with solid tumors is an infrequent occurrence. The pathogenesis of tumor‐associated eosinophilia is not well understood. Interleukin‐5 (IL‐5) is a cytokine that has been implicated in the development of eosinophilia in mice and humans. However, there is little data associating IL‐5 production with eosinophilia in the presence of tumor. We report, in a patient with locally advanced NSCLC, the presence of excessive eosinophilia and elevated serum IL‐5 levels at diagnosis. Immunohistochemical staining of the primary tumor showed large amounts of intracellular IL‐5. Both eosinophil count and IL‐5 levels normalized after surgical removal of the tumor. Tumor‐associated eosinophilia observed in this case is mediated by IL‐5. The production of IL‐5 is related to the presence of the tumor. Am. J. Hematol 2007. © 2006 Wiley‐Liss, Inc.