Katy Perry performs surprise acoustic set for fan with brain tumour

The popstar sang 'Roar', 'Fireworks', and 'Chained to the Rhythm'

Katy Perry visited a sick fan on Monday after discovering she would miss the singer’s concert to recover from unplanned brain surgery.

Grace Moore, 8, underwent surgery last week to remove a 6cm tumour.

Her older sister Tiana, 16, shared Grace’s disappointment on twitter, using the hashtag #HelpGraceMeetKatyPerry. That one tweet was retweeted 20,000 times.

The tweet attracted the attention of Katy Perry’s team who organised a surprise visit and private concert at Grace’s home with Perry using two guitars for the impromptu show before dashing off to her stadium performance in Adelaide.

The singer shared a short clip with the family to her  70 million followers on Instagram, describing Grace as her “new merch model”.

Perry is currently in Australia as part of the Witness tour. NME caught Katy Perry’s “brilliantly bonkers” live show in June, describing it as: “Visually captivating, vocally impressive, and most importantly, impossibly good fun.”

The pop singer recently revealed how the public’s reception to Witness, her fifth album, suffering from “bouts of situational depression”.

She told Vogue Australia: “Music is my first love and I think it was the universe saying: ‘Okay, you speak all of this language about self-love and authenticity, but we are going to put you through another test and take away any kind of validating “blankie”. Then we’ll see how much you do truly love yourself.'”