When you first look at a congenital nevus can you tell how much of a cancer risk it is?

Yes: A true congenital nevus (very dark and hairy, from birth) has a fair chance of having little melanomas pop up in it, but if you watch it closely and get them excised, the real danger is small. Other dark birthmarks include as nevus spilus (almost no risk) and cafe au lait spots (no risk). Physicians are very familiar with these and can let you know what's best do to. Stay proactive & thanks.

Sometimes: There is a ton of variability within skin lesions. Some very bland lesions can have cancer, and others that look very ugly can be free of cancer. Fortunately, the "abcd" of skin lesions is useful to decide which need a biopsy. Asymmetry, irregular borders, dark or irregular color, or a diameter greater than 6 mm are higher risk features. Finally, if a nevus is changing that should prompt biopsy.