Hypereosinophilia associated with cardiac rhabdomyosarcoma

Hypereosinophilia, defined as an absolute eosinophil count exceeding 1,500/mm 3 , is caused by a limited number of disorders. Its association with malignancy is a rare occurrence that typically denotes extensive metastasis and a poor prognosis. Several theories have been proposed to explain the hypereosinophilia associated with malignancy, focusing on the production of eosinophilopoietic cytokines by tumors. We describe a patient with hypereosinophilia associated with a cardiac rhabdomyosarcoma, review the etiologies of hypereosinophilia, and discuss the possible mechanisms. Am. J. Hematol. 74:64–67, 2003. © 2003 Wiley‐Liss, Inc.