How do you tell the difference between a mole and melanoma (skin caner)?

I've been swimming for about 4 months now (swim team).. outdoors. but i wear sunblock most of the time. i'm asian, and rarely burn. (only tan, and get darker and darker..) i now have tiny black spots on my arm -7 on my right arm, and 5 on my left.. i'm "pretty sure" most wern't there before (two of the black dots were always there). do i have melanoma or just more moles?

Moles don't usually just appear over night however you said you've been in the sun and that could cause them to be more noticeable.Melanoma is usually slightly red and sometimes tender.It also grows quickly-within a month it could almost double it's size,whereas a mole generally stays the same.If you are really concerned by all means get checked by a doctor

There is an ABCDE methond which is:

A Assymetric or it's not the same on both sides
B Border is rigid
C Color isn't the same
D Diameter Increase in size Report It

you need to see a doc. i had what looked like a mole, but it turned out to be skin cancer .... way back in high school.

Little early to be thinking about melanoma! Give them about one month and if no change in size or color, don't worry about it! If noticeable change in size or color, then go see doctor! But it sounds a little early to be worrying about cancer!