I had a chest X-ray in January 2016, it was identified I had a right pericardial cyst, the size of a fist, I had concerns no one had seen one and the rarity, on 2nd March 2016 I had it removed , 4 days later I was out of hospital and 11 days after the operation still on pain relief but the symptoms I was experiencing have gone, the cyst was test but benign as I read it would be. I am writing this , I am not a doctor but an ex- patient, I was petrified when no one seemed to have seen one , but delighted when I went to a heart and lung specialist in London at the Royal. Brampton in Chelsea, the specialist said he sees about one a year, it was successfully removed, hope this helps