Seborrhoeic wart. Light micrograph of a section through a seborrhoeic wart in skin tissue. Also known as seborrhoeic keratosis and basal cell papilloma, this is a common benign skin tumour. It arises from the epidermal layer of the skin. The central round area is a cyst within the papilloma. The cyst consists of concentric layers of keratin, a tough skin protein. Surrounding the cyst are the dark-stained cells of the tumour. These warts are usually found in the elderly. They are harmless, but may be removed for cosmetic reasons.