What Causes Swelling Under The Breast Along With Mild Pain In Ribs?

Hi,i have a swelling under my left breast which i have had before some months ago and was told it was probably lymphatic fluid due to surgery i have had in my armpit,but it resolved itself,and now over the past week has swollen again and is a bit bigger than it was before and i also have some mild pain in the ribs on that side.