The 50-year-old breast-cancer survivor confirmed this week she learned about the mass when she had an MRI after suffering memory lapses.
She insisted she is fine, however, in an online posting Wednesday.
"Hey everyone," she said. "Please don't worry about my 'brain tumor,' it's a non-cancerous growth. I know some folks can have problems with this kind of thing, but I want to assure everyone I'm OK. ... I'm feeling very healthy and happy, and having a great time on the road playing with my new band. I'm busy working on my next record too, which I'm very excited about ... and I'll be on The Tony Awards this Sunday. ... Really appreciate everyone's love and concern, I feel so blessed to have the support of all my fans, but I'm good -- really! Love, Sheryl."