Breast Screening

False positive results

Each mammogram is read by two specially trained radiologists or film readers, and the woman and her GP usually receive the results within two weeks.

Some women (about 4 in every hundred that are screened) are called back because the x-ray indicates that more tests are needed (NHS Breast Screening Programme – 'Helping you decide' leaflet July 2013). Women should not be surprised if they are called back and then tests show that there is nothing to worry about. Most of these women (3 out of 4) will have no problems and will continue to be screened every three years.

A 'false positive' mammogram is where something found on the x-ray turns out not to be cancer. The radiologist who read the mammogram saw a suspicious change in the breast but further tests found no cancer. These tests can include more mammograms, an ultrasound scan, a fine needle aspiration (FNAC) or a core biopsy (see 'Referral to a breast clinic').

False positives are relatively common in breast screening programmes. They occur more often in younger women, women who have had a breast biopsy or who take hormones, such as oestrogen and progesterone. The skill of the radiologist can also affect the chance of a false positive result.

Some women we spoke with were recalled for further tests after having a routine mammogram on the NHS Breast Screening Programme. These tests showed that they didn't have breast cancer, but being recalled can cause concern. 

One woman said that, when she was recalled, more mammograms were taken at the breast clinic. The x-rays showed changes in her breast tissue which were due to the HRT she had started since her last routine screen. Another woman was recalled and had a fine needle aspiration and a core biopsy. The biopsy suggested that the calcifications on her mammogram were ductal carcinoma in situ (DCIS) but, when she had an operation to remove the affected area of her breast, the tissue was reported as benign (not cancerous). Unfortunately, both these women had pre-cancerous cells detected by their next mammogram. One of these women was later found to have invasive breast cancer.

One woman was frightened when she was recalled because her mammogram showed calcium deposits. Although these turned out to be harmless, her experience of having a false positive result made her slightly anxious about subsequent mammograms. Another said she didn't feel anxious about subsequent mammograms and, if she noticed any breast changes before her next appointment, she'd visit her GP. 

The recall rate in NHS breast screening is carefully monitored in order to keep the number of false positive recalls as low as possible.

Last reviewed March 2016.

Last updated March 2016.

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