Yet, after being referred to a renowned surgeon by her doctor son-in-law, Ms Cook had three ribs and half of her lung removed in February 2013.
Now in remission five years later, Ms Cook, who believes her five-a-day 40-year smoking habit caused her illness, said: 'I never thought I'd be here today. Amazingly and against all the odds, here I am.'
She is speaking out to raise money for Cancer Research UK and encourage others to get involved in fundraising.
'It looked like my ribs had been eaten away'
Speaking of her visits to the doctor, Ms Cook said: 'I'd been back and forth numerous times, but had not been referred to hospital. By August 2012 I was desperate.
"I remember going into the surgery and yelling, 'If you don't refer me I'll call the CPS (Crime Prosecution Service)'."
Ms Cook was then sent to Norfolk and Norwich University Hospital, where a scan revealed her tumour.
She said: "When the scan came back, it looked like my ribs had been eaten away. It looked like they'd been chewed on by a caterpillar."
A few weeks later, further tests revealed Ms Cook had grade three, adenosquamous carcinoma lung cancer; a rare type of non-small cell lung cancer.
She said: "When I found out I was devastated. I just sat and cried."
'Against all the odds, here I am'
After her diagnosis, Ms Cook underwent radiotherapy and chemotherapy, which caused her to lose her hair, however, these were not enough to beat the disease.
She was then heartbroken to be told surgery was not an option, saying: 'Hearing that was devastating. I knew I needed the tumour to be cut out, to give me a chance of surviving.'
Yet hope was not lost as Ms Cook's son-in-law arranged for her to see the renowned surgeon Tom Routledge, from London's Guy's and St Thomas' NHS Foundation Trust, at his private clinic, who she describes as her 'hero'.
Mr Routledge successfully operated on Ms Cook and, after three weeks in hospital, she was cancer-free and allowed to go home.
Ms Cook said: "I went from being told in December 2012 that the cancer was effectively terminal, to having the tumour removed. I still can't quite believe everything that happened to me.
"I'm back at work and busy helping to look after my wonderful grandchildren and my rescue dogs Dudley, Tilly and Vince. My life is busy and full and I relish it all."
'She came with bravery and fortitude'
Ms Cook's surgeon Tom Routledge clearly remembers treating her, saying: "I remember Catherine very well, as her surgery was quite complex.
"She came through a difficult treatment with bravery and fortitude and it has been a pleasure for me and my team to care for her."
A spokeswoman from Norfolk and Norwich University Hospital Trust said: "We welcome Catherine Cook to get in touch with us to discuss any issues she may have in regards to her care at the Norfolk and Norwich University Hospital (NNUH)."
Ms Cooke is supporting Cancer Research UK's Race for Life in partnership with Tesco.
People can take part in one of more than 300 events across the UK and help beat cancer.