Cruel trolls have bombarded beloved comedy favourite Magda Szubanski after her shock revelation she is battling an “obscure” cancer.

The Kath and Kim star has endured a torrent of online abuse since she announced in an Instagram post on Thursday that she had stage-four mantle cell lymphoma, describing it as a “rare and fast-moving blood cancer”.

Szubanski went public in a video showing her shaven head, which she said was in preparation for treatment in which it would fall out.

In her typical, positive style, the 64-year-old smiled and laughed throughout her video, at one point cackling as she said “what are you gonna do?”

“I won’t sugar-coat it, it’s rough,” the 64-year-old wrote of her diagnosis.

“But I’m hopeful. I’m being lovingly cared for by friends and family, my medical team is brilliant, and I’ve never felt more held by the people around me.”

But her announcement has been met with an ugly wave of abuse. Some social media users have suggested Szubanski’s Covid vaccinations are the reason for her disease.

Szubanski fronted an ad for the Victorian government at the height of the pandemic – drawing the ire of anti-vaxxers and others unhappy with Covid measures. This latest trolling taps into an anti-vaccination conspiracy theory that alleges people who have been inoculated against the virus are at risk of issues such as fast-developing cancers and heart problems.

“Very sad to hear another experimental vaccine pusher has been diagnosed with something horrible. I guess you must ‘face the consequences’ of your choice now?” wrote one X user.

“I have as much sympathy for her as she had for us that said no!” wrote another.

A third said: “Turbo cancer comes to mind … Although she wasn’t so charitable with us ‘anti-vaxxers’, I still wish her the best.”

Other social media users rushed to Szubanski’s defence, with the multiple exchanges enough to keep the comedian’s name trending on X nearly 24 hours after her announcement.

“Anti-vaxxers don’t want to be treated with contempt by society, then behave abhorrently online. Magda Szubanski reveals blood cancer, then you post your cooker rubbish all over news articles,” wrote one supporter.

“Think of her and her family and friends. You’re not cookers, you are just scum.”

There was also an outpouring of support from prominent Australians. Former Australian of the Year Grace Tame led a string of well-wishers in comments on Szubanski’s post.

“Sending you all the love in the world and warm, immuno-safe virtual hugs,” she wrote.

TV presenter Lisa Wilkinson said all of Australia was behind the comedian.

“Sending love, strength and every ounce of joy you have given all of us over the decades, to help see you through these difficult times darling Magda,” she wrote.

Others to send love included entertainers Rove McManus, Peter Helliar and Julia Zemiro, along with model Megan Gale and singer Dannii Minogue.

The Leukaemia Foundation says mantle cell lymphoma affects the outer-edge – or mantle zone – of B-cells in the lymph node follicle.

It accounts for about five to 10 per cent of all non-Hodgkin lymphomas, with the average age at diagnosis between 60 and 65 years.

Szubanski said she would lie low while her immune system “takes a hammering”.

“I’ve been feeling pretty ratshit for ages. So I asked for extra bloods and – voila,” she wrote.

“The takeaway is, get tested and listen to your body.”

Szubanski is perhaps best known for winning the hearts of Australians as the sporty, unlucky-in-love Sharon Strzelecki in sitcom Kath and Kim. That sparked roles in the smash-hit movies Babe and Happy Feet (and both sequels), among others.

She first burst onto Australian screens in the mid-1980s after being picked up by ABC talent scouts who’d seen her perform in a university revue.

Her credits include sketch shows Fast Forward and critically acclaimed Big Girl’s Blouse, alongside Kath and Kim co-writers Gina Riley and Jane Turner.

The comedian was a prominent marriage equality campaigner after coming out as gay in 2012.

She used her profile to push for a yes vote in the 2017 Australian referendum on same-sex marriage, including a pivotal appearance on the ABC’s Q&A program and an address to the National Press Club.

-with AAP