I have this lump in my right upper arm, on the outside, between my triceps and biceps. Normally (like right now) it's small and I can barely feel it, but when I'm working out, especially on arms day, it gets bigger and I can see it when I look in the mirror. After my pump goes away it goes back to it's normal small size. It doesn't hurt at all unless I squeeze it. There must be a good blood supply to it seeing as how it gets bigger when the area fills with blood (like when I work out). I think it may be a lipoma. Anyone have any ideas? I suppose I should go to my doctor, huh? It's been there as long as I can remember, but recently I've kinda been freaking out cuz it looks kinda big when I have a pump (I wish my arm muscles would get bigger, instead).