A 60-year-old man with renal cell carcinoma was treated of right nephrectomy and high dose administration of Interferon-alpha (IFN) in 1990. Three and half years after operation, he complained of cough and hemoptysis. Chest X-ray showed a abnormal shadow (5.5 x 3.5 cm) in the upper lung field. On chest CT, a tumor mass with small cavity was located at S2, attended with the speculation and pleural indentation. A rough nodule suspected daughter tumor was pointed out near the tumor mass. Laboratory investigation revealed mild leucocytosis, an elevated ESR and C reactive protein. On lymphocyte subset, CD 4/8 ratio was 0.8 and NK cell activity was 11%. Immunosuppressive acid protein (IAP) in serum was 1,137 ng/ml. No organisms or malignant cells could be demonstrated in the biopsy materials or sputum. Right thoracotomy and upper lobectomy was carried out. Postoperative pathological diagnosis was inflammatory pseudotumor. Namely, the lesion was occupied with variable admixture of lymphocytes, plasma cells, histiocytes, phagocytes included hemosiderin, foam cells and whorled fibrosis. Daughter tumor was scar tissue. Now, he is well without recurrence and his immune response is within normal level. Some discussion of the literature was mentioned.