While breast cancer is the second most commonly diagnosed cancer among women in Ireland, genetic breast cancer - the type actress Angeline Jolie was at risk from - is rare, the Irish Cancer Society (ICS) has emphasised.

Around 3,000 Irish women are diagnosed with breast cancer every year, however only 5-10% of these cases are genetic.

"Genetic breast cancer is a type of breast cancer which can occur when a faulty gene is passed on from either parent. A cell needs to have a number of mistakes in its genetic code before it becomes cancerous. These mistakes or faults are called mutations," the society explained.

It pointed out that having a gene mutation ‘doesn't mean you will definitely get cancer, but you are more likely to develop cancer than the average person'.

In the mid-1990s, it was discovered that mutations in the BRCA1 and BRCA2 genes significantly increased a woman's chance of developing breast and ovarian cancer. It is now known that women who have a fault in either of these genes have a 50-85% chance of developing breast cancer and a 10-40% chance of developing ovarian cancer.

Earlier this week, Angeline Jolie revealed that she had undergone a double mastectomy after discovering that she carried a faulty BRCA1 gene. (See more here)

According to the HSE's National Cancer Control Programme (NCCP), in order to identify women at risk of genetic breast cancer, a National Hereditary Cancer Programme was established in 2011. This is building on a service that has been available for the last decade and involves diagnostic and counseling services in Dublin, Cork and Galway.

There are two groups of women who this genetic testing is available to - those who have already been diagnosed with breast cancer and those with a family member who has been found to carry the gene mutation.

As part of this hereditary programme, additional genetic testing clinics were opened in St James's Hospital and the Mater Hospital in Dublin, while a similar service is due to be opened in Cork University Hospital ‘in the coming months', the NCCP said.

"In 2012, the new clinics in the Mater and St James's Hospitals assessed and tested almost 200 women with breast or ovarian cancer for the BRCA gene mutation. This represents more than a 100% increase in the numbers of women tested nationally compared with 2011," it explained.

It noted that there had also been a ‘significant increase' in the number of women being tested who did not have cancer themselves, but did have a relative with the gene mutation.

"These figures are expected to continue to increase with the further expansion of the service. All women receive (genetic) counselling to ensure they are fully aware of the implications prior to testing," the NCCP said.

For more information on genetic breast cancer and the BRCA1 and BRCA2 mutations, click here