I'm 21 years old and circumcised.lately i noticed brown pigments on my penis shaft. Sime of them are small and other one is bigger. The bigger one is like a ring surrounding my penis (somehow like a circumcision scar). I don't know if they have been there all the time or not. I'm virgin so it is not an std. It is my first pist so i don't know if i can upload a picture. I'm a little bit worried. Can this be penile cancer, or it is common for males to have brown pigmentation on their shafts. I usually masterbate once or twice daily but not in a rough way ( i don't know why i mentioned this but it may help).