My seroma was in my armpit near my SLNB incision and it hurt, but they drained it and it came back a week or so later but after the 2nd time they drained it, it never came back 🙂 The end time though at night i would put heating pad under my arm because I also had nerve damage running down the back of my arm but I massaged it and it too went away on it's own after about a month. Surgery is traumatic for our bodies, and sometimes our bodies just get angry and don't behave nicely.