Thymoma Is an anterior mediastinal tumor, arising from the thymus, but occasionally has ectopic focus such as neck, trachea, thyroid, pulmonary hilum, lung parenchyme and pleura. Forty-two year old male patient was admitted due to progressive development of shortness of breath in 4 months. He had a history of exposure to asbestos for About 10 years duration In recent 15 years. Radiologically, multiple pleural masses were seen rom apex to diaphrAgm, with no evidence of anterior mediastinal mass,with fluid in right pleural cavity. Closed thoracotomy drainage with open biopsy were performed. Effusion cell block showed many T cell marker positive Lymphocytes & some epithelial cells compatible with thymoma, and the tissue also showed cortical type thymoma. Pleuropneumonectomy and thymectomy followed by 60 Gy radiation therapy were done and the patient is well 8 months postoperatively. The pleura is markedly thickened by the invasion of thymoma and the interstitial space of the lung tissue,but the normal appearance of thymus was present in remote area (Masaoka classification IVa). We report a case of ectopic invasive thymoma arising from the right pleura with intact thymus.