Abstract
Osteochondroma is the most common benign bone tumor. It can be classified as isolated or multiple. While the majority of osteochondromas are asymptomatic and found incidentally, they can become symptomatic during adolescence or adulthood due to mechanical irritation, nerve compression, spinal cord compression, or vascular injury. In this article, we present a case of a 14-year-old patient who experienced spontaneous hemothorax caused by bleeding from a diaphragmatic laceration incurred by a costal exostosis on the right eighth rib. A preoperative chest CT scan revealed a bony projection from the rib and bloody effusion in the thoracic cavity, highlighting the possibility of bloody pleural effusion due to costal exostosis. It is important to note that costal osteochondromas are a rare cause of thoracic injury and can lead to laceration of the lung, diaphragm, and/or pericardium. Surgical intervention should be considered for symptomatic rib osteochondroma, and we advocate for prophylactic surgical removal of intrathoracic exostosis even in asymptomatic patients, in order to prevent potential complications.