The 26-year-old winger, who has also played with Brisbane, Perth and Adelaide, was told by a specialist to "forget football" and instead concentrate on his health.
Adelaide-born Armiento said he was diagnosed with stage-two Hodgkin's lymphoma in March 2024 after his Phoenix teammate Nikola Mileusnica urged him to see a doctor about a persistent cough.
An x-ray revealed a nine-centimetre mass in his lung.
In a video posted on the Wellington club's website, Armiento said he asked his oncologist about when he could play again and was quickly shut down.
"The first thing I said was 'when can I play football again' and he said, 'don't worry about football'.
"I think that's the first time I've probably broken down there and then because when you hear cancer you think your life's ending.
"It was pretty crazy because you hear a lot of stories about people getting diagnosed with cancer, but you never think it's going to happen to yourself."
He underwent two months of "intense" chemotherapy back in Adelaide followed by radiotherapy, before being given the all-clear.
"That really opened my eyes. It was pretty scary to be honest," he said.
His absence from the field had financial ramifications with Armiento cut by Brisbane, forcing the Professional Footballers Australia players' union to step up.
"Unfortunately, I got a message from Brisbane when I was doing my treatment that I wasn't going to be given a new contract," he said.
"Because it was a non-football injury as well they weren't obliged to help me medically and the cost of going through cancer is quite a bit.
"This is where the PFA were amazing ... they helped me massively and 'm so grateful I had them on board."
Armiento got himself fit and was signed to play in the Italian Serie C with Turris before linking with the Phoenix, scoring two goals in three appearances this season.
"I went over to Italy and I enjoyed my time there but it was the right time to come back this year because I'd gotten away from all of the cancer talk," he said.
"Now I've come back and I'm loving my time at Wellington.
"It is just the perfect time to come out and tell this story, not for people to know what was going on, it's for others for people who are suffering what I was suffering and think 'shit, he can get through it, so can I'."
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