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BRCA1/PALB2-associated breast cancer
This condition involves an elevated risk of developing breast cancer, and potentially other cancers, due to specific genetic variants. It is typically passed down in families, affecting both men and women, and warrants specialised genetic counselling and management within the NHS.
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Overview
BRCA1/PALB2-associated breast cancer refers to breast cancer that arises because an individual has inherited a pathogenic (disease-causing) variant in the BRCA1 or PALB2 gene. These genes play crucial roles in maintaining the integrity of our DNA. When they don't function correctly, cells are more likely to develop harmful genetic changes that can lead to cancer. Individuals with these inherited variants have a substantially higher lifetime risk of developing breast cancer compared to the general population [PMID:33671879].
While breast cancer itself is common, the inherited forms linked to BRCA1 and PALB2 are considered rare within the broader breast cancer landscape. Understanding the genetic basis is important because it can influence cancer surveillance, treatment choices, and risk-reducing strategies for the affected individual and their family members. Recognition of these genetic factors aligns with the NHS Genomic Medicine Service goals of providing personalised healthcare.
Symptoms & clinical features
The primary symptom of BRCA1/PALB2-associated breast cancer is the development of breast cancer itself. This typically presents with the same signs and symptoms as other types of breast cancer, which may include a new lump or thickening in the breast, a change in the size or shape of the breast, skin changes (like dimpling or redness), nipple changes (such as discharge or inversion), or pain in the breast or armpit. Importantly, these symptoms do not inherently distinguish between an inherited cancer and a sporadic (non-inherited) cancer.
However, there are clinical characteristics that might suggest an underlying genetic cause. These include breast cancer diagnosed at an unusually young age, multiple primary breast cancers in the same individual, or a strong family history of breast cancer (especially if it affects several close relatives or involves both breasts) and other associated cancers. For BRCA1, there is also an increased risk for ovarian cancer. For PALB2, there may be a slightly increased risk of ovarian and pancreatic cancers [PMID:22097368]. Male breast cancer in a family may also be a red flag. These factors often prompt a referral for genetic assessment.
Video: Is cancer in your genes?
Affected organs
The primary organ affected in BRCA1/PALB2-associated cancer is the breast. Pathogenic variants in BRCA1 and PALB2 significantly increase the lifetime risk of developing breast cancer. For women, this includes both invasive breast cancer and, less commonly, some types of pre-invasive breast disease. Men with these variants also carry an increased, though lower, risk of male breast cancer.
Beyond the breast, BRCA1 pathogenic variants are strongly associated with a substantially elevated lifetime risk of ovarian cancer [PMID:33671879]. There may also be a moderately increased risk of other cancers, such as prostate cancer and pancreatic cancer, with BRCA1. For PALB2, while the breast cancer risk is prominent, there may be a more modest increased risk for ovarian cancer, pancreatic cancer, and possibly melanoma [PMID:22097368]. These associations highlight the broader impact these genetic changes can have on various organ systems.
Risks & severity
The severity of breast cancer, once it develops, can vary greatly, irrespective of its genetic origin. However, having a pathogenic variant in BRCA1 or PALB2 significantly increases the *lifetime risk* of developing the disease. For individuals with a BRCA1 variant, lifetime breast cancer risks can range from 45% to 85%, and ovarian cancer risks from 20% to 60% [PMID:33671879]. Breast cancer often develops at a younger age in BRCA1 carriers compared to the general population. For PALB2, the lifetime risk of breast cancer in women is estimated to be between 40% and 60%, with some studies suggesting it can be as high as 70% by age 80, placing it closer to the risk associated with BRCA2 [PMID:22097368].
These are substantial increases compared to the general population's lifetime breast cancer risk, which is approximately 1 in 7 for women in the UK. The exact age of onset and penetrance (the likelihood that a person with the variant will develop the condition) can be influenced by other genetic factors, lifestyle, and environmental exposures, meaning that not everyone with a pathogenic variant will develop cancer. The increased risk extends to male breast cancer and, to varying degrees, other cancers as well.
Genetic causes
BRCA1/PALB2-associated breast cancer is caused by inherited pathogenic variants in either the BRCA1 gene or the PALB2 gene. Both genes provide instructions for making proteins that are critical components of the DNA repair machinery within our cells. Specifically, they are involved in a process called homologous recombination, which is a highly accurate method for repairing double-strand breaks in DNA, preventing genomic instability [PMID:31252119].
The BRCA1 gene (Breast Cancer Type 1 Susceptibility Protein) produces a protein that plays a key role in DNA repair, cell cycle control, and regulating gene expression. When the BRCA1 protein is faulty due to a pathogenic variant, DNA damage may not be repaired correctly, increasing the likelihood of uncontrolled cell growth and cancer formation. The PALB2 gene (Partner and Localizer of BRCA2) provides instructions for a protein that acts as a molecular bridge, connecting BRCA1 and BRCA2 proteins. This partnership is essential for the effective repair of DNA damage. A pathogenic variant in PALB2 disrupts this crucial repair pathway, leading to a similar increase in cancer risk as seen with BRCA1 or BRCA2 variants, albeit typically with a slightly lower penetrance than BRCA1 [PMID:22097368].
- PALB2 partner and localizer of BRCA2PALB2 (partner and localizer of BRCA2) encodes a protein essential for DNA repair, working closely with BRCA1 and BRCA2 to maintain genome stability.
Inheritance pattern
BRCA1/PALB2-associated breast cancer follows an autosomal dominant inheritance pattern. This means only one copy of the gene needs to have a pathogenic variant for an individual to have an increased risk of developing cancer. If a parent has a pathogenic variant in BRCA1 or PALB2, there is a 50% (1 in 2) chance with each pregnancy that their child will inherit the variant.
Since it is an autosomal condition, the risk is the same for both sons and daughters. Individuals who inherit the pathogenic variant have an increased risk of developing cancer; however, not everyone who inherits the variant will develop cancer during their lifetime (this is known as incomplete penetrance). Family members who do not inherit the pathogenic variant do not have this increased genetic risk and cannot pass it on to their own children.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of BRCA1/PALB2-associated breast cancer relies on the confirmation of a pathogenic variant in either the BRCA1 or PALB2 gene, typically through genetic testing. This testing is usually offered within the NHS to individuals with a strong personal or family history of breast, ovarian, or other associated cancers that meet specific criteria. Referrals for genetic assessment are primarily made by oncology teams, breast clinicians, or general practitioners to clinical genetics services.
Genetic testing involves taking a blood or saliva sample, from which DNA is extracted and analysed to look for specific changes in the BRCA1 or PALB2 genes. The NHS Genomic Medicine Service (GMS) provides diagnostic genetic testing using established national pathways, often under specific R-codes for germline testing in cancer predisposition. The results are interpreted by specialist laboratories and communicated by genetic counsellors or clinical geneticists, who can explain the implications for the individual and their family.
Management & lifestyle
Managing BRCA1/PALB2-associated breast cancer risk involves a multidisciplinary approach focused on early detection and risk reduction, tailored to the individual's specific genetic variant and family history. Within the NHS, individuals with a confirmed pathogenic variant are typically enrolled in enhanced surveillance programmes. For women, this often includes annual mammography and MRI scans of the breasts, starting at a younger age than standard screening, to detect cancers at an early, treatable stage [PMID:33671879].
Risk-reducing surgical options may also be discussed. These can include prophylactic (preventative) bilateral mastectomy to significantly reduce breast cancer risk and risk-reducing salpingo-oophorectomy (removal of ovaries and fallopian tubes) to reduce ovarian cancer risk, particularly for BRCA1 carriers. Chemoprevention, using certain medications to lower cancer risk, may also be considered. Lifestyle advice, including maintaining a healthy weight, limiting alcohol intake, and regular physical activity, might also be part of a comprehensive management plan. All management decisions are made in consultation with specialists, including oncologists, surgeons, and genetic counsellors.
UK care pathway
In the UK, individuals suspected of having an inherited cancer risk, such as for BRCA1/PALB2-associated breast cancer, are typically referred to an NHS Clinical Genetics service. This referral may come from their GP, breast clinic, or oncology team. Clinical geneticists and genetic counsellors provide expert assessment, discuss testing options, and interpret results. Genetic testing for these genes follows nationally agreed criteria, detailed within the NHS Genomic Medicine Service (GMS) pathways, often using specific R-codes for germline predisposition to cancer.
The GMS aims to ensure equitable access to genomic testing and personalised care across England. If a pathogenic variant is identified, the clinical genetics team will coordinate with other specialists, such as breast surgeons and oncologists, to develop a comprehensive, individualised management plan. Support from genetic counsellors is also available for family communication and cascade testing.
Frequently asked questions
How common are BRCA1 and PALB2 pathogenic variants?
Pathogenic variants in BRCA1 and PALB2 are considered rare in the general population. While exact prevalence figures can vary, they are some of the most common causes of hereditary breast cancer.
If I have a BRCA1 or PALB2 pathogenic variant, will I definitely get cancer?
No, inheriting a pathogenic variant means you have a significantly increased lifetime risk of developing cancer, but it does not mean you definitely will. This is called incomplete penetrance. Many factors, including other genetic modifiers and lifestyle, can influence this risk.
Can men be affected by BRCA1 or PALB2 pathogenic variants?
Yes, men can inherit BRCA1 or PALB2 pathogenic variants. They also have an increased, though generally lower, risk of developing breast cancer compared to females, and may have an increased risk of other cancers such as prostate or pancreatic cancer.
What kind of screening is recommended for people with a BRCA1 or PALB2 pathogenic variant?
For individuals with a pathogenic variant, enhanced surveillance typically involves regular mammograms and MRI scans of the breasts, often starting at a younger age than routine population screening. This is to help detect cancer early when it is most treatable.
How does genetic testing for BRCA1 and PALB2 work in the NHS?
If you meet specific criteria, your GP or specialist can refer you to an NHS Clinical Genetics service. Genetic testing typically involves providing a blood or saliva sample, which is then analysed for pathogenic variants in these genes. Results are discussed with a genetic counsellor or clinical geneticist.