A 39-year old man was referred for evaluation of a left sided tumor in the region of the third and fourth rib. Computed tomography revealed a slightly enhancing costal tumor with mainly intrathoracic expansion. Calcifications inside the tumor were present. Assuming a chondrogenic tumor of unknown dignity, en bloc tumor resection and reconstruction of the chest wall was performed. By means of the histopathological examination the diagnosis of a chondrosarcoma grade I was made.