Case reports: ossified mass of the rotator cuff tendon in the subacromial bursa.

Unlike calcification, ossification is infrequent in the rotator cuff. We describe the clinical, radiographic, and pathologic findings in 64-year-old man with an ossified mass arising from a calcified portion of the rotator cuff tendon within the subacromial bursa. Mechanical stress and ischemic events are possible causes of cartilage formation followed by endochondral ossification, producing a mass causing outlet impingement.