Occasionally, direct extension from contiguous structures such as infected rib, costochondral cartilage
, sternum, shoulder joint, through the chest wall from a tuberculous pleurisy, or via abrasions in the skin can pass infection into breast.
Al Shahed, "Premature tracheobronchial, laryngeal and costochondral cartilage
calcification in children," Clinical Radiology, vol.
The slight inspiratory pain Anne had described where the sternum joined the costochondral cartilage
and vertebrochondral rib ends worsened to where the ribs and boney structures of the chest "felt tight and made it difficult to breathe".