fluids in sac around the lungs after chemotherapy

can you please  advise or explain why the fluid gets around the lung sacs after labectomy surgery  and after chemotherapy ?
I had been diognized with lung cancer non- small cell . LOwer lung on the right side was removed. I went thru 4 month of chemo therapy and 45 days of radiAtion .
I stiLl find that there is no cancer in lung on the left side the surgey took place. However we discovers .Just one small cell on far right side about 10 mm. Most intriguing thing I find puzzling to me there was no fluid around my lungs six weeks ago. In less than six weeks, in the CT scan , we find fluid around the lungs in the lung sacks  about 25% covered on right lung.Is this curable?Is this an infection or cancereous?
What is the best medical option?  WHo in this country has done more reesearch in this area succefully treat this fluid issue or drain it successfully?   Need your exeprt advise ASAP
Sara1000

[katarina777]

Dear sara, this here is a breast cancer forum, and you may want to go to the general cancer forum, or lung cancer forum, (I am not sure if there is one of the latter) to post your question.

regards,

KATRIN