Bifid intrathoracic rib: a case report and classification of intrathoracic ribs.

Bifid intrathoracic rib is a very rare anomaly of the ribs that is characterized by an osseous prominence of a rib into the thoracic cavity. We report a 21-year-old woman with bifid intrathoracic rib arising from the anterior-lateral portion of a depressed 4th rib, based on findings from chest radiography and computed tomography (CT). This is only the second reported case of this type of intrathoracic rib worldwide.