Etiology: not clear; exposure of affected area to sunlight; chromosomal abnormalities in the skin, occupational exposure to tar and / or pitch; compromised immune status; exposure to HPV (types 9, 11, 13, 16, 18, 24, 25, 33, 37, and 57)
Epidemiology: over age of 60; uncommon in under age of 20 and darker-skinned individuals; more often in males then females
Pathogenesis: originate from pilosebaceous glands; solitary lesion; firm, skin-colored, reddish papules that grow rapidly; spontaneous regression of lession; sun-exposed skin of face, neck, and upper extremities; dome-shaped nodules; smooth shiny surface with central crater containing core or plug of keratin; edge of vermilion border of lower lip; NOT found on mucous membranes within oral cavity