New study in mice points to why melanoma spreads — and perhaps how to prevent metastasis

In some melanoma patients, the tumor cells stay in the skin where they started, never migrating via the blood to a vital organ such as the brain or lungs — and if they do leave the skin, getting no farther than the lymph nodes before dying during the arduous journey. In other patients, the malignant cells dash out of the skin like sprinters at the starter’s gun, fighting off the perils in the bloodstream until they reach organs where they will soon prove lethal.

Why some melanomas turn fatally metastatic and others on Wednesday, however, offers a peek inside: Melanoma cells are more likely to spread through the body if their surface bristles with molecules that grab a certain chemical in the blood and usher it into the cell, where it increases the cells’ chance of survival.