Hi Christine, lymphoedema is a bit unpredictable, if you have had a full clearance you are at more risk but plenty people have full clearance of nodes and have been fine but the risk is a lifelong one. I only had WLE and four nodes out but went onto to develop lymphoedema but I also had a seroma and there does seem to be a link between having seromas and lymphoedema but no-one has come up with a reason why....not a huge amount of research on lymphoedema unfortunately.
My seroma took the form of getting out of bed one morning and my poorly boob literally exploded ! It was like something out of an alien film, I stood there and swore rather a lot. But i was lucky(?) in a way in that I had a small hole as an outlet so no need for aspiration, I just went to the distict nurse to literally milk the gunk out, lasted about a week and was fine and dandy after that and no infection.
Good luck with your continuing recovery and hope your seroma sorts itself out .
Sandra x