In November, she went to have a swollen gland checked, and was sent to hospital for scans and a biopsy straight away.
"I had been feeling perfectly fine .. Within 19 hours I got a phone call to say things were looking concerning."
Ms Souness was referred to Christchurch otolaryngologist (head and neck surgeon) Dr Rob Allison for treatment even before her test results were in. "Planning had already started to remove my thyroid, parathyroids, part of my windpipe as it looked like cancer had eaten some of my cartilage away," she said.
"The nerve on one side to my voice box had to be removed, and some lymph nodes. I didn't have a diagnosis but was told I had a tumour and it looked like I had two cancers.
"By late November, the pathologist report confirmed sclerosing mucoepidermoid carcinoma with eosinophilia [SMECE], a rare cancer.
"The hardest thing was to tell family and friends ... My two daughters coped very well as my youngest had a tumour removed at age 11. We have laughed and cried together."
Ms Souness had an eight-hour operation and spent days with her chin stitched to her neck during recovery, but recently found the cancer had spread to her lymph nodes.
It is likely to keep recurring and if it reaches the lungs, a patient's life expectancy is around three months.
Ms Souness will start an intensive course of radiation on January 27 and is also trying alternative therapies to enhance her treatment.
"I want live and I am willing to try anything."
As the treatments are costly she has started to fundraise, and hopes to get enough money together to go to a cancer centre in Texas.
She also wants to raise awareness about thyroid cancer and find others who have dealt with it.
Every lump 'needs to be checked'
Sclerosing mucoepidermoid carcinoma with eosinophilia is a cancer that occurs mainly in women with a background of thyroid problems including hyperthyroidism and thyroiditis.
It can spread either through the lymphatic system or the blood stream.
"It's very rare, I've never seen a case before," said Natalie Souness' otolaryngologist, Dr Robert Allison. "I'm not aware of any others in New Zealand.
"It is something that has only been recognised in the last 15-20 years ... there are probably less than 10 or 20 cases in the world."
Dr Allison said it was hard to diagnose and difficult to give a prognosis because of the small number of other cases.
"It can grumble away for many, many years. It can spread. But it's hard to say what the prognosis is as it's so uncommon." Dr Allison said while the cancer Ms Souness was battling was rare, thyroid cancer in general was increasing.
He said there needed to be more awareness around thyroid cancer, which did not get as much publicity as other forms like breast or prostate cancer.
"The most common symptom is a lump in the neck," he said. "Most thyroid lumps are benign but a large number are malignant.
"Every lump needs to be checked, by ultrasound or needle test."
Make a donation
To make a donation to Natalie's cancer treatment fund, visit www.givealittle.co.nz/cause/fightwithme.
If you know of anyone else who has been diagnosed with sclerosing mucoepidermoid carcinoma with eosinophilia, email anna.leask@nzherald.co.nz