A Friend Of Mine Had To Be Admitted To Beth

A friend of mine had to be admitted to Beth Isreal in Boston , He had to have a tube inserted in his chest to drain fluid from his lungs. A few days later he was sent home. The next day his primary care Dr called to inform him the fluid in his lungs tested positive for cancer, He said it was inoperable? he said it was coming from someplace other than his lungs and had yet to be determined. He goes for more tests this week,
Is it possible to determine all of that from a test of the lung fluid.