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. 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 think this is the cause). Thanks in advance.