I would phone your Breast care nurse tomorrow - it is not always your own surgeon who will drain it. If you are not in pain it would be ok to wait till Wednesday, but there again his clinic may be full up. I had two of these like you and different people drained it each time, in fact when the nurse drained it was less painful than when the surgeon did it! Try popping a hot water bottle under you arm, or if you have one of those wheat filled pillows that you put in the microwave that can help too. There was a recent thread on here on seromas which gave other advice too.
I had MX and ANC ten days ago. My surgeon drained a seroma on Thursday evening, but the fluid has come back again and it's probably more now than when I had it drained last week.
He's not got a clinic again until next Wednesday - is it OK to wait that long to see him or should I be getting in touch with the hospital? It's not painful but just really uncomfortable.
