Rapidly growing, even boardered, uniform colored brown spot on neck. Seeing derm in 3 weeks. Gp concerned about skin cancer. Low risk its melanoma? I'm 21

ABCDE of melanoma. Check out http://www.webmd.com/melanoma-skin-cancer/abcds-of-melanoma-skin-cancer as quick reference to ABCDEs of skin cancer. You didn't mention size but it's change/growing thus evolving. While melanoma is rare in 21yo, I agree that evaluation is key. May need biopsy for absolute proof.