It was an emotional day for his mum, Alisha Konig, and stepdad Scott Phillips, who were by his side at The Children's Hospital at Westmead in Sydney.

William, a kindergarten student at Evatt Primary who is "obsessed with Lightning McQueen", has been diagnosed with neuroblastoma, the tumour sitting on top of his adrenal gland.

Alisha said William was admitted to hospital in late August with appendicitis. A scan the next day found the mass growing on the gland. Further tests at Westmead revealed the cancer was affecting an artery carrying blood to his organs.

Alisha, an aged care worker, had to quit her job to be with William in Sydney.

"The doctors pretty much advised with William going through chemo and being immuno-suppressed, even if I could work, it probably wouldn't be a good idea because I am exposed to all sorts of bugs and infections that I could be bringing home," she said.

Her partner Scott, a night-shift worker in the transport industry, is technically still employed, but is in Sydney to help care for their two-year-old daughter and Alisha's older son. His leave runs out next week and they are concerned about how they will pay their bills and rent in Canberra.

The family is staying at the Ronald McDonald House in Sydney to be close to William.

Alisha said William would have four cycles of chemotherapy and they were likely to be in Sydney for three months.

"If the tumour has shrunk away from his main artery, they will attempt surgery and then radiation," Alisha said.

"But William's tumour is a bit of a tricky one that they haven't really seen before, in the sense it's growing in a mass and it hasn't metastasised like an aggressive tumour, but its genetic make-up is very aggressive."

Alisha said her son was "a little trooper" whose bubbly personality had not been dimmed by the treatment.

"He's a little darling," she said.

A GoFundMe page has been started to support the family.

Alisha says they do not expect help but any was gratefully received.

TheGoFundMe page is gofundme.com/f/financial-support-for-williams-neuroblastoma.

The family is also remaining connected with supporters through the Facebook page William's Journey through Neuroblastoma.