Cutaneous malignant melanoma

 In the lower epidermis, melanocytes produce melanin, the pigment that gives skin its color. Exposed to the sun, melanocyes make more pigment causing skin to darken.

Unrepaired DNA damages skin cells triggering mutations, causing skin cells to multiply rapidly and form malignant tumors.  Curable if detected early, but each year in the U.S. ~10,000 people die of this type of cancer.