The 50-year-old singer recently joked that her 'brain's gone to shit' after she forgot the lyrics to her song Soak Up the Sun during a performance in Florida.
She told the Las Vegas Review-Journal that she went to see a doctor in November when she became concerned: 'I worried about my memory so much that I went and got an MRI,' she told the publication. 'And I found out I have a brain tumour. And I was like, 'See! I knew there was something wrong.''
The rocker says that 'it gives me a fit' but her medical team have assured her not to worry because it is benign.
Sheryl says that forgetting her lyrics is not new and at a gig in the 1990s she couldn't remember the intro to A Change Would Do You Good.
'Not only could I not remember the first line, I couldn't remember the first line to any of the verses,' she recalled. I started laughing so hard! And I looked over at my guitar player, and he's bent over like he's gonna just start peeing.' Sheryl battled breast cancer six years ago and is mother to sons Wyatt and Levi.