Breast Cancer Cells in fluid around heart and in lungs

[MoShell]

My mother in-law was in the hospital and they found fluid around her heart that drained into her lungs. They tested the fluid and it came back with Breast cancer cells. She had breast cancer 4 years ago and they removed her breast but she never underwent treatment. She had a pet scan done last week, and the pet came up nagitive for any cancer cells. So the only place there is cancer cells is in the Fluid in her lungs and around the heart. She is currently undergoing chemo and antibody treatment, they are treating her as if she has breast cancer. What happens now? What happens when the fluid goes away, does the cancer go away? Does this mean she may have lung cancer? If anyone could help me out I will be very greatful.
Thank you Michelle.

[Cleveland Clinic]

Dear Michelle, When fluid develops around the heart and lungs evaluations are done to determine what the cause is.  One of the evaluations is to send a sample of the fluid to the laboratory where a pathologist looks at the cells from the sample under the microscope to find any abnormal cells.  The finding of breast cancer cells in that fluid is an indication that breast cancer cells have spread to this area.  This would be treated as breast cancer that has spread (not as lung cancer). The goal of treatment of breast cancer that has spread is to control the disease and symptoms of the disease for as long as possible.   Her oncologist will monitor how she is responding to the treatment, as well as how she is tolerating the treatment.