This is tough because of the paucity of data to answer the question. In my practice, I recommend patients who develop a new primary melanoma undergo standard-of-care therapy for the new melanoma (e.g., WLE +/- SLNB). 

I agree though, sometimes it can be tough to distinguish whether a new cutaneous lesion is new cutaneous metastases or a second primary. In patients who have had prior extensive exposure to the tanning bed, I often see these patients presenting with multiple primary melanoma lesions - again, it can ...