What are the chances of my melanoma coming back if i use sunblock and stay out of the sun?

Risk goes down: You do decrease your chances to get melanoma, but can still get it, especially if you have family history of melanoma. Mucosal type melanoma has no association to sun exposure at all, fortunately they are rare.

Depends: This depends on the depth of the melanoma and the amount of normal skin that was removed from around the melanoma. Also having one melanoma make it more likely that you could develop an additional melanoma. Sunscreen will help, but often the damage was already done to your skin decades before.

Melanoma : Statistically one is more likely to develop additional melanoma after a previous melanoma has been diagnosed . Sun protection , self exams, and routine skin exams by your dermatologist.

Two issues: Sunblock won't change the risk of a treated melanoma from recurring (coming back), but it will reduce the risk of future skin cancers, which any melanoma patient is at a higher risk of. So protect yourself from the sun using not just sunblock, but shade, clothing and smart sun behavior. Also continue surveillance exams for the melanoma and self skin exams.