A mother-of-two says she is "appalled" after being told she will have to wait 17 weeks to see a consultant over her breast cancer fears, breaking guidelines that it should be 10 days.
Breast cancer is the most common form of cancer in the UK
Theresa Debono, 40, said people were being treated "terribly" by the NHS.
Her case has been taken up by her MP, former Welsh health minister Jon Owen Jones, who said he was furious over a "life or death" issue.
Labour Welsh Health Minister Jane Hutt said she was "extremely concerned", and the local health trust said it did not have the staff and resources to deal with all its cases.
Ms Debono, from the Roath area of Cardiff, has been waiting 10 weeks for a mammogram, and would have to wait a further seven before a lump on her breast can be diagnosed.
Ms Debono, who has a son and a daughter, said: "I think it's terrible the way people are being treated.
"The way I look at it, I could have breast cancer, I'm worrying about something that I might not have. I haven't really spoken to my daughter about what's wrong with me, she knows there is something because of the way I am.
"I don't want her to worry, she's going to college now. She will be upset. I just hope something can be sorted out quickly for
myself and for other women who have been waiting.
"I blame the Welsh Assembly, but then they put money into the hospitals - who
runs the hospitals?" she added.
Ms Debono, who is on a waiting list at the University Hospital of Wales, Cardiff, said she would be willing to be treated outside the city, or even in England.
Mr Jones' sister was diagnosed with cancer this year
Mr Jones said breast cancer had affected his own family. "My sister had this diagnosis 18 months ago. She was operated on within a fortnight," he said.
"Things are going very well for my sister now but she lives in London, and my constituent is in Cardiff. As far as I know it's unheard of anywhere else."
Ms Hutt said she was aware of the case, had replied to a letter from Mr Jones. She said she also knew that he had been promised a detailed reply from the health board, which " are the organisations responsible for providing services in the city."
But, she added that as the minister and the AM for the Vale of Glamorgan: "I have been extremely concerned about this aspect of breast care service in Cardiff and Vale over recent weeks.
"During August I met with the trust's new chief executive, Hugh Ross, and trust chair, Simon Jones, and made breast care services the first item on the agenda for discussion.
"As a result, the trust has instigated a five-point action plan to address the issues raised, including short-term measures and a longer term strategy."
Ms Hutt said diagnostic breast care was vitally important and had to be a top priority.
"Services in the rest of Wales are currently out-performing those in Cardiff and the Vale by a large margin. Waits in Swansea for suspected breast cancer, for example, are between 10 and 14 days.
"It is not acceptable to me, as health minister, that such variation in service should have arisen and I will remain in close contact with those responsible until satisfied that a speedy resolution has been achieved.
"In the meantime, I remain deeply concerned at the case which has been highlighted today," she added.
In a statement, Hugh Ross, chief executive of Cardiff and Vale NHS Trust, said: "I share the minister's deep concern about the length of time that patients are waiting to be seen by the trust's breast service."
He added that the trust received around 80 referrals each week but only had the resources and staff to deal with 60.
"Everyone in Cardiff and Vale NHS Trust believes that rapid consultation and treatment in relation to breast cancer is of paramount importance."
Mr Ross said they were considering sending their referrals to other breast centres.
"What we really need, however, is a sustainable long-term solution to our
capacity problem," he added.
Breast cancer is the most common cancer among UK women, although survival rates are increasing due to early detection and improved treatments.
According to guidelines issued to GPs, patients should be urgently referred and seen by a consultant within 10 working days.