My Husband Has Been In The Hospital 3 Times In

My husband has been in the hospital 3 times in past 6 weeks. First time they took 500 cc fluid off left lung. One week later he had a stent for blocked artery. The next week he was back in the hospital. Left lung had more fluid than first time. Test on fluid show large amounts of atypical mesothelio cells. Last xray stated moderate left basilar pleural parenchymal opacities. The doctors have not come up with answers as to what is wrong. Please, any information would be greatly appreciated. He is home now and I am scared the fluid will come back again