Jimmy Buffett's cause of death revealed

Singer Jimmy Buffett, who died Friday at the age of 76, battled skin cancer for years before his death, according to a statement on his website.

Buffet suffered from Merkel cell cancer, which he was diagnosed with four years before his death, his website said. 

Merkel cell cancer is very rare, according to the National Cancer Institute. Risk factors include sun exposure, having a weak immune system and being older than 50. It tends to grow quickly and spread at an early stage to nearby lymph nodes and then to lymph nodes or skin in other parts of the body, including the lungs, brain, bones and other organs.