By Jane Elliott BBC News health reporter

Dr Elizabeth Howard's asthma masked her symptoms

Elizabeth Howard, a GP, missed her own cancer for eight months.

By the time it was diagnosed, her tumour was wrapped around her lungs and her heart.

Later this month Dr Howard will be taking part in Cancer Research's Race for Life - it is her way of thanking those who gave her a new lease of life.

Even medical professionals, she says, can be fooled when cancers do not follow the rules.

Research

Two years after a rare diagnosis of Non-Hodgkin's lymphoma in her chest the 35-year-old GP, from Romford, Essex, says she "cannot believe" it happened.

Instead of a death sentence this scan was my last-minute salvation Dr Elizabeth Howard

When she first became ill, she and her doctors misjudged her chronic cough and the tightness in her chest as signs her asthma was getting worse.

The steroid tablets she was taking partially treated the lymphoma, easing symptoms and giving false reassurances.

Signs

Dr Howard tried to rationalise her problems: the tiredness was down to stress and sleep deprivation and the hot sweats a product of the heatwave of 2003.

Logically there was no reason for her to think she had cancer. She saw her chest consultant regularly and had even had an X-ray earlier that year.

Her doctor had suggested she have her chest scanned, but Dr Howard decided against it.

"Knowing that most of the time no cause is found I suddenly felt I was being a hypochondriac or 'being stupid' and let it drop.

"I thought 'What's the use? It'll only come back negative and waste a precious scan'."

When Dr Howard had lost about 35% of her lung function, her specialist still unsuspecting, offered to send her a CT scan.

"Knowing that most of the time no cause is found I suddenly delt I was being a hypochondriac or 'being stupid and let it drop.

"I thought 'What's the use? It'll only come back negative and waste a precious scan'.

"My breathing was so bad that I could hardly finish sentences and my patients were sending me home."

Dr Howard's condition deteriorated further and she was referred to a second chest consultant who decided she needed a CT scan, an ear, nose and throat (ENT) opinion and other tests.

Her ENT consultant had her neck and chest scanned urgently and found the tumour, which by this time measured 10 centimetres by 18.

I thought, how can I be a 'good GP' with so many letters after my name yet miss my own cancer for over eight months? Dr Elizabeth Howard

Dr Howard underwent three types of chemotherapy and a stem cell transplant.

'Patients sent me home'

Despite having lost her hair twice, the cancer did not go into remission until she was given further treatment.

Although Dr Howard berates herself for not spotting her own condition, she realises that it was thoroughly masked by her chronic asthma.

"I thought, 'How can I be a good GP with so many letters after my name yet miss my own cancer for over eight months?'

"Cancers have expected patterns of behaviour. The urgent cancer referral guidelines are based on these common patterns.

"Then there are ones like mine which decide they aren't going to be part of the crowd and go and hide somewhere it is difficult to find them.

"In my case my only swollen glands were deep in my chest where I could neither see nor feel them.

The 'Race for Life' has been running for 11 years

"Other cancers, like bowel and ovarian, also play hide and seek, giving vague symptoms on and off for months before giving any definite clue to their identity."

Dr Howard now lives each day as it comes.

No one can tell her what the next few years hold, especially as her body does not seem to follow all the usual patterns of the disease. Long-term prognosis is indefinable.

"Once I had the diagnosis there was a chance to do something about my illness, so instead of a death sentence this scan was my last-minute salvation.

"I have already beaten the odds. The next five years remains to be seen.

"There is no crystal ball for any of us. If there were I am not sure I'd want to look, in case I don't like the answer. "