In a heartbreaking Instagram post shared on Tuesday evening, Johnny shared a picture of himself and his girlfriend Tahnee Simms, writing: "After an unexpected week of seizures and excruciating headaches it is with a heavy heart that i have to let you know i now have another huge battle ahead of me as my brain cancer has returned."
He added: "Though i will dig deep and beat this sht disease again 👊🏽💜 #fckcancer"
A number of Johnny's former co-stars and other celebrities who know the talented actor flooded the comments section, with fellow Home and Away star Penny McNamee leading the tributes writing: "Will be praying for you Johnny. You have so much love and support behind you. Xxx."
Dan Ewing, who also acted alongside Johnny on the hit soap added: "Let's get after it Ruffo!!"
Lincoln Lewis was also among the celebs who wrote: "F### man we're all here with you and cheering you on!!! Sending all our love, support and good energy brother!! You got this."
Georgie Parker wrote: "Yes you will. All my love to you Johnny."
While Carrie Bickmore added: "Oh Johnny....Sending so much so love. Kick it's arse 👊🏻"
Johnny spoke to Now To Love just a few weeks ago as he threw his support behind the Starlight Children's Foundation.
The actor and musician is leading a team of twelve 'superhero' children, known as the 'Amazon Playmakers', from hospitals around Australia who will test toys ahead of Christmas.
They will collaborate with the online shopping giant to reveal the top 100 toys and trends for the holidays. And to top it off, all toys purchased on shopping frenzy days Black Friday to Cyber Monday (27 November –30 November) will see $5 donated to the Starlight Children's Foundation.
Johnny also hinted at the release a new single, which we can expect to hear in the coming weeks.
Our thoughts are with him as he drives forward in this difficult time.
This article originally appeared on Now To Love.