A couple of months ago I noticed a fairly large lump/sore on the shaft of my penis. The lump was dark purple in color, was located in the middle of the shaft, and has somewhat painful or sore when I touched it. However, the lump disappeared just two or three days after it had first presented itself. I've been somewhat concerned that it might've been the beginnings of penile cancer. However, since I'm only 18 years old, am circumsized, and have no other risk factors for penile cancer, it seems pretty unlikely (penile cancer is rare enough as it is). However, I'd like to get someone's opinion on it nevertheless. Based on the fact that the lump was fairly large, dark purple, somewhat painful, and only lasted for a couple of days, does this sound more like cancer or more like something else that isn't nearly as serious? Are cancerous lumps usually dark purple in color, are they usually painful, and do they normally last for only a couple of days?