I am 77 and have crusty patches on my breasts, back and stomach. Could they be cancerous? Dr Ellie Cannon replies: It is unlikely. These sound like seborrhoeic keratoses – harmless skin growths that affect around three-quarters of people over 70 and often appear as rough, crusty patches in shades of tan, brown or black that can grow several centimetres wide. Although sometimes called seborrhoeic warts, they’re not caused by a virus as actual warts are.