Identifying the unexpected factor that contributes to melanoma risk could lead to a new prevention strategy including better suncreams, the researchers claim.
There is already an established higher risk of melanoma among people with red hair and fair skin because of a lack of natural protection against ultraviolet (UV) radiation.
But the team believe the pigment predominantly found in red-haired, fair-skinned individuals may itself be a second contributor to melanoma.
"We've known for a long time people with red hair and fair skin have the highest melanoma risk. These new findings do not increase that risk but identify a new mechanism to help explain it," said Dr David Fisher of Massachusetts General Hospital.
"This may provide an opportunity to develop better sunscreens that address this pigmentation-associated risk while continuing to protect against UV radiation.
"We're excited to have a new clue to help better understand this mystery behind melanoma."
The study is published in the journal Nature.