fluid in lungs, shoulder and back pain with tumor

I am a US citizen living in Mexico City with my fiancee's family. My mother in law appears to have various problems and I am very frustrated with the medical system since she hasn't received a diagnosis yet. 6 months ago it was confirmed that she has a tumor on her cheekbone. First she was told it was a bone tumor, and later just a tumor on the bone. Then, about 4 months ago, her lungs started filling up with water and she has experienced a lot of shoulder and back pain. After a recent topogrphy of her lungs, the doctor told her it looks bad in her shoulder bones, lungs and the part of the liver they could see. A biopsy of the tumor came back as ''bland tissue''. They plan to remove the tumor soon but even after physically removing water from her lungs, they consider it risky. Basically, the medical system appears inadequate. She is 50 years old without a family history of cancer or personal history of medical problems. She does not smoke. Only symptom besides pain and fluid in lungs is weightloss. Blood tests and test of lung fluid, as well as mamogram have come back negative.

Is this probably cancer? What origin is most likely? If it is cancer and it has spread, is there still hope for a cure? Does it sound like something curable? Could this be something that isn't cancer? Any suggestions? Advice given the public healthcare system?