Performer Lorna Luft collapsed back stage at a concert in London and was taken to hospital.
The 65-year-old suffered the blow and has now been diagnosed with a brain tumor after the episode on Friday night.
Her rep, Victoria Varela, said that 65-year-old Luft collapsed backstage on Friday night and was rushed to the hospital, where she was given an initial diagnosis of a brain tumor.
Varela revealed the singer's husband, Colin Freeman, had been concerned that she was forgetting lyrics and a monologue.
Luft was undergoing further tests at London's Chelsea and Westminster Hospital.
The actress and singer has been in remission from breast cancer, which she has been battling for six years.
RadarOnline.com previously reported that Minnelli and Luft have had a strained relationship over the years.
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