[A case of thoracolithiasis].

Many kinds of tumor shadows have been reported on chest X rays in recent years, some of which are difficult to diagnose. A 72-year-old man was admitted to our hospital for further tests, because of an abnormal shadow recorded on a chest X ray on a routine health examination. Chest CT scan demonstrated a round mass lesion, about 2cm in diameter, at the pleural surface of the S6 segment of the right lung. Our attempt at CT guided percutaneous lung needle biopsy failed because the needle was unable to penetrate the tumor, resulting in right pneumothorax. Later, a tumor was located in the basal part of the right lung, which was confirmed by CT scan. Video-assisted thoracic surgery (VATS) was performed, and a white 2-cm nodule in the right pleural cavity and two grayish-white 2-3-mm nodules on the right pleural surface were removed. The cut surfaces of these nodules showed a small black core surrounded by white concentric structures. Histologically, a small quantity of coal dust and many histiocyte-like cells were found in the core, surrounded by acidophilic fibrous connective tissue. These findings were consistent with thoracolithiasis, which is a rare disorder but one that requires diagnostic differentiation from peripherally located lung tumors.