Calcific tendinitis in unusual sites associated with cortical bone erosion.

Five cases of calcific tendinitis with radiographic evidence of cortical bone erosion are presented. All five cases arose at unusual sites: two at the pectoralis major insertion on the proximal humerus, two at the insertion of the gluteus maximus, and one at the insertion of the adductor magnus. Biopsy was performed in four cases and revealed areas of histiocytic infiltration, amorphous spherules of calcification, and areas of giant cell reaction extending into the cortex. To our knowledge, calcific tendinitis presenting with radiographic evidence of bone erosion has not been reported previously.