Under a microscope, the cells on three-year-old Sienna Cook’s arm looked suspiciously like ‘adult melanoma’ – but the dermatologist dismissed it as impossible.

Her worried mum Shawnee, 30, from Perth, was told it was likely just a benign lump and would need to be cut out. Doctors added that while it could certainly ‘become cancerous’ it ‘wasn’t yet’ so there was no rush.

They were wrong. Now Sienna, a bubbly little toddler, is mid-way through a gruelling series of cancer treatments after the potentially deadly disease spread to her lymph nodes.

While rare, most forms of melanoma in children can’t be prevented as they are genetic and caused by a mutation. Doctors are learning more about these tumours, which are often called ‘spitzoid melanomas’.

The most common symptom is a sudden ‘small lesion’.

Speaking to FEMAIL, Shawnee revealed the family’s frustrating experiences with medical professionals who, until they landed at the children’s hospital, seemed to dismiss Sienna and her little red sore every step of the way.

At first the bump, which appeared in June, looked like a little bite – but months later it started to look ‘infected’

‘I am still in disbelief. I am scared and angry. I trusted the professionals – they had her life in their hands and got it wrong,’ she said.

The melanoma, which is a genetic variant and not caused by the sun, appeared on the then two-year-old’s arm in June, 2023.

It wasn’t brown, didn’t have rough edges or dark spots and didn’t grow rapidly like typical melanomas do.

The family were in Bali on holiday and it looked like your average mosquito bite.

‘I don’t have any photos of it back then because it didn’t look different enough for me to even think about taking a photo,’ she said.

The little round bump never seemed to go away. Then, at the end of August, it started to noticeably annoy Sienna.

It was itchy, would hurt when she played with her five-year-old brother and started to scab over and bleed.

So, like all parents do when they notice something amiss with their bubs, Shawnee decided to take her little girl to the GP to get it checked out.

He assumed it was some kind of staph infection and gave her a cream to try. Then a week later he gave her another one. A week after that he tried some oral medicine. Nothing worked.

Sienna actually had melanoma – it has been cut out and she’s had a second operation to remove lymph nodes where the cancer had spread

Shawnee was losing faith and it vanished altogether when the doctor took a photo and started ‘Googling it’.

‘I said “I don’t mean you any disrespect but I feel like you don’t know what it is”,’ she said.

She then asked for a referral to a dermatologist. It was now late October.

The skin specialist offered her a cream but she rejected that and opted to go back to get the sore scraped instead.

‘A few weeks passed and I got a call saying that under the microscope it looked like adult melanoma but that wasn’t right, given her age,’ she said.

‘They did more tests and told me it was a benign lump and that I should get it cut out because it could become cancerous.’

This is when she started to worry so she called the surgeon who had been recommended and his staff said the results weren’t urgent. They would see Sienna after Christmas.

Shawnee is pictured here with her kids on that Bali holiday – her son Byron, five, has had a suspicious mole removed since his sister was diagnosed though results aren’t back

She went in when they reopened on January 15.

‘At this point I was stressed because they said it could turn cancerous but everyone was telling me not to worry,’ she recalled.

The mum became even more stressed after receiving calls from the dermatologist to see if she had cut it out – and then urging her to do it quickly.

‘I thought “hang on you said it wasn’t urgent why do you keep calling me?”‘ She said.

The surgeon said the results looked benign and said he could cut it out for $6000 or the family could wait two weeks and the hospital would cut it out for free.

‘We decided that everyone had been telling us it was benign and it was only a two week wait and we didn’t have $6000 on hand so we would wait,’ she said.

Then it took the practice over a week to make out the referral, despite multiple calls from Shawnee and the dermatologist.

On February 20 they arrived for their first consultation at the hospital.

The family, which includes Brayden’s eight-year-old from a previous relationship, have been super stressed for weeks

Doctors here were far more alarmed by the results which confirmed active ‘adult melanoma’ cells.

‘He looked at her arm, felt her lymph nodes, looked at the records and then asked us to give him a minute,’ she said.

‘He left the room and came back 30 minutes later to let me know they had just had a cancellation and they could operate the next day.’

Sienna’s dad Brayden, 33, asked the doctor to be straight with them. Shawnee remembers words like oncologist being thrown around and the doctor revealing he wasn’t comfortable ruling out melanoma because of her age.

The lump was cut out and seemingly divided medical opinion.

Teams of doctors were consulted including specialists in Perth. They came to the conclusion it had to be treated like melanoma.

A PET scan showed a hot spot in her lymph nodes. 

Then the terrified toddler, who had started to develop a fear of the hospital, was put in a straight-jacket like brace in an imaging machine so doctors could determine which lymph nodes needed to be removed and tested.

‘She was in the scan for three hours, it was the most traumatic day, the camera was so close to her face but she couldn’t move and she was screaming at us for help,’ she recalled. ‘She said “save me mummy” and I just had to sit there.’

The test failed so they took another approach and found the lymph nodes in her arm needed to be removed.

‘They had to take all of them out – they usually don’t do that,’ she said.

In the meantime Sienna’s big brother Byron had a mole pop up out of nowhere.

‘We asked them at the hospital what to do. we didn’t want to go down the same road,’ she said.

The doctors have removed the lump and aren’t taking any chances – given the disease is hereditary.

Sienna’s appointments continue and the ‘fiery princess’ has developed attachment anxiety and bawls when she can’t see her mum.

‘She has changed so much – we got married in November and she stayed at grandmas and didn’t bat an eyelid,’ she said.

‘I dropped her there when my son had his procedure and she bawled.’

Sienna has had a few operations to cut out the melanoma, increase borders, fix drains and remove lymph nodes and will start immunotherapy soon.

This could cause complications down the track including Hepatitis, Type 1 Diabetes, thyroid issues and Heart Disease/Failure.

And given the nature of the disease there’s no way to know if they ‘got it all’.

‘It could be travelling, which means it could pop up somewhere else,’ Shawnee said.

Shawnee’s sister started a Go Fund Me to help support the family support Sienna. Shawnee has stopped working though Brayden continues to run his air con company.

Shawnee wants parents to be on the lookout for sores which don’t heal and push for answers if they are ignored 

At  one point the sore looked like it had an ulcer inside 

Shawnee wishes she knew about childhood melanoma and understood more about its appearance – but admits even doctors she has met since are fascinated.

‘The whole family have had their skin checked since she was diagnosed. The doctor who checked my husband and cut something out asked to see photos and the pathology report and admitted he wouldn’t have thought it was melanoma,’ she said.

She says if the disease was caught when she first went to see the doctor – or even when abnormal cells were first noticed – it may not have spread.

The family have also thanked the Australian Skin Foundation for their support since Sienna was diagnosed.

‘We are at the end of the first part of her journey. We still have a long way to go,’ Shawnee said.