[A case of thyroid medullary carcinoma-like tumor of the lung with amyloid stroma].

A 58-year-old man with history of productive cough and mild exertional dyspnea for several years was admitted to our hospital because of abnormal shadow on chest radiograph. Bronchofiberscopic examination revealed a polypoid tumor almost completely obstructing the right main bronchus. Bronchoscopic biopsy specimens showed amyloid-like deposits in the connective tissue surrounded by epithelium-like tumor cells with squamous metaplasia, but no diagnostic findings. Malignant tumor was suspected and right upper lobectomy was performed. The surgical specimen revealed nests of tumor cells surrounded by amorphous eosinophilic substance, which was confirmed to include amyloid fibrils by electron microscopy. A few tumor cells contained argyrophil granules by Grimelius staining, and some showed PAP staining for calcitonin. There was no evidence of involvement of other organs including the thyroid gland during the four year postoperative follow-up period. This case was diagnosed as thyroid medullary carcinoma-like tumor of the lung, which is a bronchopulmonary carcinoid-related tumor.