What Causes Fluid In Lungs On Chest X-ray And Swollen Neck Lymph Nodes?

Hi, my husband has been though much testing in the past 2 weeks. It all started with a swollen supraclavicular lymph node. Then a week later one on the other side became enlarged. After a week, he went to the doctor who put him on amoxicillin. During this stage, he got extremely tired, and began running low grade fevers. After the 10 day regime with no results, he went for blood work, which all came back normal. Next, a chest xray, which showed fluid in his lungs and something in his chest. A ct scan revealed the swollen lymph nodes in his neck and either a mass or swollen lymph nodes in his chest. He went to get the fluid drained off his lung. They took a gallon off and said they would take the other gallon within a week (he has an appt. Monday). This fluid was tested and lymphocyte cells were present. He had a biopsy of the first swollen lymph node a couple of days ago and they said the results would be in within 7-10 days. The doc. said something about a type of lymphoma after the initial look at the biopsy. We now have an appt. with an oncologist this week. I feel like we are not getting enough info. They say whatever is in his chest is pushing on an artery, which is causing the fluid. I don't understand why no one knows what this is. If this is lymphoma, is there any insight as to what type it might be? Is this something where he will need his lung drained every week? He has been feeling short of breath with back pain due to the fluid. He is 32 years old and other than this has always been in great health. Any detailed info. would be appreciated. Thanks