“…The pleura and the pericardium develop from the same coelomic cavity: that is why Herbig, Ganz, and Vieten (1952) believe that the term 'pleuro-pericardial cyst' gives the most accurate description of the tumour. Ringertz and Lidholm (1956) contended that there may sometimes be a connexion between the cyst and the pericardium, so that it becomes difficult to tell whether the resulting growth is a true cyst or a diverticulum.…”