[A case of pseudolymphoma of the lung with cough and fever].

This case report presents a 48-year-old woman who had been suffering from cough and fever for 5 years. A large mass in the right lung was pointed out. Even after various examinations, we couldn't resolve the difficult diagnostic problems involved, but it was clear that there were no signs of a malignant tumor. We suspected a large benign tumor or pulmonary sequestration. Right lower lobectomy was performed and histological examinations of the resected tumor revealed lymphoproliferative disorder. Microscopic examinations of the specimen disclosed monotonous lymphoid cells proliferation (small to medium size) without definite lymph follicles or germinal centers. Lymph follicles were clearly demonstrated with the immunoperoxidase method. These findings were interpreted to be consistent with what has been recently called pseudolymphoma of the lung and prompted discussions on the reasonableness of criteria for the diagnosis of various pseudolymphoma and effective immunological examinations for the clarification of the etiology.