Lung cancer with eosinophilia in the peripheral blood and the pleural fluid.

A case of lung cancer associated with eosinophilia in the peripheral blood and pleural fluid is reported. A 55-year-old man with a tumor in the right lower lung lobe and right pleural effusion was admitted to Ehime University Hospital. Histology of specimens biopsied under a bronchoscope revealed that he had poorly differentiated squamous cell carcinoma. On admission, his peripheral blood leukocyte count was 11,500/microliters with 7.8% eosinophils and the pleural fluid showed a high eosinophil count (60.5%). After chemotherapy, blood eosinophilia disappeared and the pleural effusion was decreased with the reduction of the tumor. The patient's serum had the activity to stimulate eosinophil proliferation in human bone marrow cell culture, suggesting that the tumor may have produced an eosinophil proliferating factor.