Seborrhoeic wart. Light micrograph of a section through a seborrhoeic wart in human skin. This is a common benign (non-cancerous) skin tumour also known as basal cell papilloma or seborrhoeic keratosis. It arises from the epidermal layer of the skin. Within the wart are a number of cysts (round), within which are concentric layers of keratin, a tough skin protein. These warts become more common with age. They are harmless, but may be removed by freezing (cryotherapy) for cosmetic reasons. Magnification: x570 when printed at 10 centimetres wide.