When Kate Callaghan felt a lump in her breast, she never thought it could be stage four breast cancer - and neither did her doctors.

As a holistic nutritionist, personal trainer and lifestyle coach, doctors considered the health-conscious 35-year-old mum-of-two too low-risk to have cancer.

"I am healthy ... I was breastfeeding for four years, which is meant to be protective against breast cancer. If you look at all the risk factors, I tick none of them, if you look at all the preventative things to do, I tick all of them," she said.

"I think [doctors] put those things together and decided I didn't need to worry."

SUPPLIED Kate Callaghan with her husband Aaron and their two children, Ed and Olivia.

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Callaghan, who is mum of 4-year-old Olivia and 2-year-old Ed, felt a lump in her left breast in June.

"I thought it would just be lumpy breasts from breastfeeding," she said.

"I was heading overseas in July so thought if it's still there when I get back, I'll go and get it checked out."

SUPPLIED Mum-of-two Kate Callaghan said her cancer tumours had shrunk after three weeks of natural treatments in Mexico.

When she returned from her trip, she went to the doctor, who said the lump was nothing to worry about and to just keep an eye on it.

Callaghan said she didn't feel comfortable with that so she went to another GP for a second opinion. He also said it was probably nothing to worry about, but did refer her to Dunedin Hospital for an ultrasound.

After a month of asking her doctor's office when her appointment was, she called Dunedin Hospital directly, who told her they never received her referral.

"I expected a referral - you trust your doctors to a certain degree ... I probably should have pushed harder in hind-sight," Callaghan said.

"I think they have acknowledged that they should have acted sooner as well. I have been angry ... but I need to let go of that now because it's not helping where I am."

She couldn't say if a months' delay would have made a difference to the progression of the disease.

"My breast lump would have been smaller, it might not have spread to my lymphs and it might not have spread to my liver or as extensively. Given that it takes 50 days for breast cancer cells to replicate, and I would have lost about 60 days, so there was some [cancer] growth in there."

After an initial examination, a Dunedin Hospital breast surgeon told Callaghan he also thought it was unlikely to be cancer.

"And then we did an ultrasound, we did a mammogram and we did a biopsy and four hours after initially talking to him, he said 'I'd be 90 per cent sure that this is cancer'."

SUPPLIED Kate Callaghan is a holistic nutritionist, personal trainer and lifestyle coach.

A few days later, on November 7, the biopsy results confirmed the breast cancer diagnosis. Callaghan was booked in for mastectomy, chemotherapy and radiation, however, a CT scan on November 18 showed the cancer had spread to her lymph nodes and liver so she was no longer eligible for treatment, only palliative care.

"Basically mainstream [medicine] here have said anything we do for you now is just keeping me well while I wait to die, which doesn't sit well with me because I feel fine so I'm not about to go on something that's going to make me feel sick and [lose] all that quality of life.

"I'm not against mainstream at all, I was going to go down that track ... we had it all planned out until they said no, we can't do that anymore, this is all we can offer you, so then I decided to look into other things."

SUPPLIED Kate Callaghan has been diagnosed with stage four breast cancer.

Callaghan is currently raising funds for alternative treatment at the Hope4Cancer healing centre in Mexico. She hopes to leave for the Mexico clinic in the next few weeks for her first treatment, which will cost around $73,000 for a three-week stay, excluding travel expenses, followed by two more shorter visits. She plans to take her husband, Aaron, and her Mum Robyn Edleston​ with her for support.

She said the treatment will include measures to boost the immune system, such as eliminating microbic pathogens, nutrition, detoxification and emotions. She planned to use a combination of mainstream and alternative medicine when she returned to New Zealand, she said.

"It's just getting my body in a better position to receive it first."

Nearly $170,000 has been raised in four days for Callaghan, who has 24,000 followers on Instagram. She has received many messages of support, she said.

"It's overwhelming and very humbling. The support that everyone has offered in many ways is just so unbelievable."

Callaghan said one way she made peace with her diagnosis was the hope it would help others.

"Even sharing [the diagnosis] on my social media initially encouraged many other women to go an get their breasts checked," she said.

"Just one person getting checked or being proactive and pushing for followups if needed, makes it all worthwhile."

Donations can be made on Callaghan's givealittle page.