What is melanoma, who does it affect and how can people avoid it?

Some health advice recommends year-round sunscreen – but too much shade can be harmful too. Photograph: Dusan Stankovic/Getty Images

Over the past two decades, cancer cases in the UK have been rising twice as fast for people under the age of 50 compared with older age groups: almost 100 seemingly fit and healthy young adults in Britain discover they have a tumour every day.

Melanoma, is one of the three main types of skin cancer along with basal cell carcinoma – which starts in the basal cells of the lower epidermis, the outermost layer of skin – and squamous cell carcinoma, which starts in the squamous cells of the outermost layer of skin.