 [ Symptoms ] the is a dark mark and lump on my arm that not a bruise its sort of oval shaped in my armpit area on the backside of my arm its been there for monthsat least 3 now this skin over the lump is darker than the skin surrounding it & smooth idk what to say about the borders because theres really no def border it just looks like a smear of darker color and its not itchyflaky or anything the lump is really firm& isnt malleable i can not move it at all& theres been no pain from it i just need to know if it sounds like something i should get checked out [ Disease ] yes get it checked out medically there is really no way to determine the significance of a lump based solely on a description