A<unk>  is a non-cancerous (benign)<unk> in tumour that originates from cells in the outer layer of the<unk> in. Like liver spots,<unk>  are seen more often as people age. The tumours (also called lesions) appear in various colours, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than across. They can often come in association with other<unk> in conditions, including basal cell carcinoma. Rarely<unk>  and basal cell carcinoma occur at the same location. At clinical examination the differential diagnosis includes warts and melanoma. Because only the top layers of the epidermis are involved,<unk>  are often described as having a "pasted on" appearance. Some dermatologists refer to<unk>  as<unk>  warts", because they resemble warts, but strictly speaking the term "warts" refers to lesions that are caused by human papillomavirus.
Seborrheic keratosis
Basal-cell carcinoma
Hydrocarbon keratosis
Melanoma
Arsenical keratosis
Wart
Actinic keratosis
Reactional keratosis