Malignant fibrous histiocytoma associated with peripheral blood eosinophilia. In vitro studies demonstrating tumor-derived eosinophilopoietic activity.

Peripheral blood eosinophilia is a well-recognized paraneoplasia in many kinds of hematological and nonhematological malignancies. We report the case of a patient with a malignant fibrous histiocytoma. With increasing tumor burden, the patient developed a marked peripheral blood eosinophilia. Using an in vitro assay for growth of eosinophilic colonies, both the serum and the tumor of the patient proved to contain an eosinophilopoietic activity.