I have a tan spot on my penis shaft. don't know how long it has been there. slightly smaller than a pencil eraser. it doesn't appear raised. ?

Unsure: It's hard to say since you're not sure how long it's been there, however, since it's not painful, seems to be a color not that far off from the rest of your skin, and is not raised, I think these are things that point to it likely being benign. However, to be safe,you should probably be getting skin checks once a year from your dermatologist and he or she can take a look at this to be sure as well

Have exam: It would be best to have an exam and then a correct DX will be made. It is impossible to make a DX without exam