Thymoma displaying endobronchial polypoid growth

Two rare cases of invasive thymoma with prominent endobronchial polypoid growth are presented. Chief complaints of both patients, women aged 56 and 62 years, were blood streaked sputum and cough. A large mass shadow located in the mediastinum and lung field was seen on chest x-ray film and an endobronchial polyp was found by bronchoscopy in each patient. Histologic features of the bronchial biopsy specimens were highly suggestive of thymoma. The tumors resected surgically exhibited a unique manner of extension, in which the lumina of bronchi of various sizes were occupied and obliterated by a part of the tumor contiguous to the mediastinum. These tumors were diagnosed histologically as invasive thymoma, predominantly epithelial type, and mixed lymphocytic and epithelial type.