Blood and bone marrow eosinophilia in malignant tumors. Role and nature of blood and tissue eosinophil colony-stimulating factor(s) in two patients.

Eosinophilia of the blood and bone marrow may be encountered in patients with disseminated malignancies. It is unrelated to the histologic type of the tumor but usually reflects its aggressiveness and prognostic outlook. Its pathogenesis is controversial. The presence of eosinophil colony-stimulating factor(s) in serum and malignant tissue extracts was evaluated in two cases of malignancies accompanied by marked blood and bone marrow eosinophilia. When compared with controls, serum and tumor tissue extracts stimulated the growth of G, M, and Eo colonies in semisolid cultures of human bone marrow. Such stimulating effect was inhibited by the addition of antibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3. Thus, the colony-stimulating factor(s) play a role in the pathogenesis of the eosinophilia associated with some malignant tumors, and these factors appear to include GM-CSF, interleukin-3, and probably others.