ABSTRACT
Although the papillary thyroid carcinoma generally follows an indolent course characterized by slow growth and abscence of distant metastasis, distant metastases to extrathyroid organ may occur in the lung, bone and brain in about 5% of patients. The lung metastases are usually diagnosed by plain X-ray, chest CT and 131I whole body scan. However, we present a case of papillary thyroid carcinoma with microscopic pulmonary metastasis that could not be detected by conventional method, such as chest X-ray, chest CT and 131I whole body scan. A 62-year-old female visited due to traumatic hemopneumothorax. In the pathology of resected tissues from lacerated lung parenchyme, metastatic papillary carcinoma was diagnosed without evidence of abnormality in radiologic examination and we diagnosed and treated an asymptomatic papillary thyroid carcinoma.