My mother was found to have TB in 1950 and the procedure they used was to remove her lung and replace the space with 22 plastic balls.
In the early 1980's she visited an osteopath complaining of an aching shoulder. Further investigations showed that one of the balls had taken a stroll!
It was decided to remove the offending ball and its friends and allow the cavity to fill with liquid.
What you see here is one of those removed balls.