Stage 0 melanoma in a mole vs not in mole life expectancy difference

The short version: I can't give you a life-expectancy difference, because the evidence in front of me doesn't measure survival by where a stage 0 melanoma started.

The closest real data compares mole-associated melanomas to melanomas on normal skin, but it counts how thick they were, not how long people lived. In one 15-year series of about 2,000 melanomas, 8.4% arose in a mole and 91.6% started on normal skin [1]. The mole-associated ones were thinner on average, 0.83 mm versus 0.97 mm [1]. Thinner is better, but thickness is a stand-in for outcome, not the outcome itself.

Notice the twist: stage 0 was actually more common among the normal-skin melanomas, 35.2% versus 24.5% [1]. So the "caught earlier because it was watched" story doesn't hold up cleanly here.

For stage 0 itself, the records show it is treated by complete removal, and upstaging to invasive disease at excision happened in 23% of 570 lesions across the reviewed studies [2]. That is the number that matters for your question, not the mole origin.

My call: no life-expectancy difference can be stated from this evidence, and the mole-versus-normal-skin distinction is not the lever that decides survival at stage 0. Confidence: low.