Does a mammogram miss tumours?

No cancer screening is absolutely 100% fail-proof. The mammography screening, however, is considered to be a very effective method for detecting early stages of breast cancer.

Women 50 years of age and up can have the x-ray examination through the Mammography Screening Program every two years. During this examination about 75 to 80 percent of breast cancer, which will develop within two years, is discovered.   The majority of detected tumours are still in their early stages, have not yet spread to the lymph nodes and have a good prognosis.  Gentler treatment methods can be used and there is a better chance of recovery.

However, breast cancer may also develop within the two years between examinations, which has not been detected by mammography or, in rare cases, despite the strict quality assurance, has been missed by the mammogram or assessed as benign. Therefore, even if your screening mammogram is normal, it's still important for you to monitor your breasts for changes and contact your treating physician if you find any abnormalities such as a noticeable lump.