Seborrheic keratoses tend to:
- Start as small, rough bumps, then slowly thicken and develop a warty surface
- Have a waxy, stuck-on-the-skin look
- Be brown, though they range in color from white to black
- Range in size from a fraction of an inch to larger than a half-dollar
- Form on the chest, back, stomach, scalp, face, neck, or other parts of the body (but not on the palms and soles)
- Cause no pain — some itch
Seborrheic keratoses. Some seborrheic keratoses look like stucco splattered on the skin. 
Seborrheic keratoses. Like his father, this man saw many of these growths appear on his skin.
Learn more about seborrheic keratoses:
Images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.