If you have previously been diagnosed with melonoma insitu and you have many miles how likely is it that you will get it again and spread somewhere?

Not clear: Not sure what you mean by miles. Melanoma in situ is not likely to spread. Your greatest risk is for developing a new melanoma. You need to follow good protection from the sun and continue to follow up with your dematologist.

Melanoma risk: Most of the time, melanoma starts on normal skin, not in a mole. Giant congenital moles have a higher risk of melanoma. Having a lot of moles is a risk factor for melanoma, not a precancerous condition. 5-10% of people with history of melanoma will get another melanoma. Any changing or symptomatic (itchy, painful, bleeding, crusting, etc) mole needs to be seen by dermatology asap.

Increased risk: Having a history of melanoma does increase your risk of developing another one. You should see your dermatologist at least every 6 months for a complete skin examination.