Unprotected and / or excessive exposure to ultra violet (UV) radiation.
Occupational exposures to coal tar, pitch, creosote, arsenic compounds, or radium.
Family history of skin cancer.
Multiple or atypical moldes.
Severe sunburns as a child.
Any change in the skin, especially in the size or color of a mole or other darkly pigmented growth or spot, or a new growth.
Scaliness, oozing, bleeding, or change in the appearance of a bump or nodule.
The spread of pigmentation beyond its border, such as dark coloring that spreads past the edge of a mole or mark.
A change in sensation, itchiness, tenderness, or pain.