Abstract
A 46 year-old housewife visited our hospital because of an abnormal chest X-ray finding. The abnormal shadow arose from the 5th thoracic vertebra and extending vertically adjacent to the 10th rib, along the mediastinum in the left lung field. The size of the shadow was approximately 15cm in length and 5mm in width. Since it had osseous density and located within the thoracic cage, it was diagnosed as supernumerary intrathoracic rib. CT revealed the continuity from the rib to the parietal pleura. As she had no signs or symptoms, no therapy was performed. Intrathoracic rib is an extremely rare anomaly, in that only 25 cases have been reported in the world and only one in Japan to date.
