Regular mammograms are critical for the early detection of cancer, but for women with dense breasts, the disease can be harder to see.
It's already prompted a new screening approach in parts of Australia and the US, and similar changes are wanted here.
Nichola Turenhout never imagined she'd be celebrating her 50th birthday with a stage three breast cancer diagnosis.
"[It was a] huge shock, I felt like the whole bottom of my world fall out," she said.
But, above all else, she felt let down by the country's free breast screening programme, which ultimately delayed the detection of her tumour.
"Mammograms are failing 50 percent of women with dense breasts, and I happen to be one of them," Turenhout said.
When a woman's breast is mostly fatty tissue, cancer is easier to see on a mammogram. Denser breasts have more fibrous and glandular tissue, which appears white on scans, making it harder to spot the disease.
Not only that - women with the condition also have a greater risk of breast cancer.
"That's why it's really important that women are told if they have dense breasts so they can understand their level of risk, be more vigilant and told about other options for detecting," Breast Cancer Aotearoa Coalition chair Libby Burgess said.
One in ten women have extremely dense breasts, like Turenhout and require further MRI and ultrasound testing.
But those receiving free mammograms are not told this information unless they pay to go private.
"It's incomprehensible that this life-saving specialist knowledge is being withheld," Turenhout said.
"We hope that this Government will understand the need to put more resources into BreastScreen Aotearoa to allow this really important information to be gained and to be shared with women," Burgess said.
The Royal Australian and New Zealand College of Radiologists has recently updated its position on the matter, to recommend the mandatory measurement and reporting of breast density during screening and diagnostic testing.
It's a new approach that's already underway in parts of Europe, the US, Canada and Australia.
The National Public Health Service director of prevention, Alana Ewe-Snow said: “it is part of our workplan to review the evidence on breast density reporting and make recommendations, but we still have a lot of work to do.
"If the evidence supports the introduction of additional imaging for women with dense breasts this would require further financial investment.”
An investment, that Turenhout says will save lives.
"The truth is, finding out your breast density isn't going to kill you but not knowing could very well be fatal," Turenhout said.
