Philadelphia chromosome-negative chronic myelogenous leukemia with prominent eosinophilic component

A patient with Philadelphia chromosome-negative chronic myelogenous leukemia and hypereosinophilia was found at autopsy to have multiple splenic tumors composed exclusively of mature and developing eosinophils. This finding indicated a clonal proliferation of the eosinophils and supports the concept that the hypereosinophilia was also a component of the leukemic process.