ann, I had a doutful growth on the middle of my back, which I couldn't see - now and again it bled, it used to catch on my waistband - and as rojash suggsted, mine was dark and raised. The GP took a look at it closely under a magnifying glass, could immediately see that it was a keratosis and nothing more sinister, so he arranged for it to be taken off at our local minor surgery clinic. However, just to be on the safe side, they send the sample for histology - just waiting for the results now.
I wouldn't try to tell the difference myself - if in doubt, get it looked at.