PALB2 is a gene that helps repair damaged DNA in your cells. When it works normally, it plays a critical role in preventing cancer. But when someone inherits a harmful mutation in one copy of this gene, their lifetime risk of breast cancer can reach as high as 81%, placing PALB2 alongside BRCA1 and BRCA2 as one of the most significant breast cancer risk genes known.
How PALB2 Protects Your DNA
Your cells constantly sustain DNA damage from normal metabolism, environmental exposures, and simple errors during cell division. One of the most dangerous types of damage is a double-strand break, where both sides of the DNA helix snap apart. To fix this, cells rely on a repair process called homologous recombination, which uses the undamaged copy of a gene as a template to restore the broken one accurately.
PALB2 acts as a bridge in this process. Its full name, Partner and Localizer of BRCA2, describes exactly what the protein does: it physically connects the BRCA1 and BRCA2 proteins so they can work together at the site of a DNA break. Without functional PALB2, the repair machinery can’t assemble properly, and cells start accumulating the kind of genetic errors that lead to uncontrolled growth. Tumors that develop from PALB2 mutations show the same patterns of genetic instability seen in BRCA1- and BRCA2-related cancers.
Breast Cancer Risk for Women
The cancer risk tied to a PALB2 mutation varies significantly depending on family history. A 2025 study from the National Institute of Environmental Health Sciences found that PALB2 carriers with a family history of breast cancer had a lifetime risk of up to 81% by age 80, comparable to what BRCA2 carriers with family history face. Without a family history, the numbers drop considerably: about 9.4% by age 50 and roughly 30% between ages 50 and 80.
This wide range matters because it means a PALB2 mutation alone doesn’t seal your fate. The combination of the inherited mutation plus other genetic and environmental factors determines where any individual falls on that spectrum. It also means that screening and prevention strategies can be tailored based on personal and family context rather than applying a one-size-fits-all approach.
Risk for Men
Male breast cancer is rare in the general population, affecting about 0.1% of men over a lifetime. But PALB2 mutations increase that risk roughly sevenfold, based on multiple studies. One large Italian study of over 760 men with breast cancer found a similar sevenfold increase, and an international study of 524 families with PALB2 mutations confirmed the pattern. PALB2 is now recognized as the second most commonly mutated gene in male breast cancer, behind only BRCA2.
While a sevenfold increase sounds alarming, it’s important to put it in context. Seven times a 0.1% baseline still translates to a relatively low absolute risk. Still, men with a known PALB2 mutation benefit from awareness and clinical breast exams, since male breast cancer is often caught late simply because no one was looking for it.
Pancreatic and Ovarian Cancer
PALB2 mutations don’t only affect breast tissue. Carriers also face elevated risks for pancreatic cancer (2% to 5% lifetime risk) and ovarian cancer (3% to 5% lifetime risk), according to current NCCN guidelines. These numbers are lower than the breast cancer risk but still meaningfully higher than the general population’s baseline. Pancreatic cancer in particular is difficult to detect early, so knowing you carry a PALB2 mutation can influence screening decisions.
How PALB2 Mutations Are Inherited
PALB2 mutations follow an autosomal dominant inheritance pattern for cancer predisposition. That means you only need one altered copy of the gene (inherited from either parent) to have an increased cancer risk. If one of your parents carries a PALB2 mutation, you have a 50% chance of inheriting it. The gene sits on chromosome 16, and both men and women can carry and pass on the mutation equally.
Having one mutated copy doesn’t mean your DNA repair shuts down entirely. Your second, normal copy still produces functional protein. Cancer typically develops when the second copy is also lost or damaged in a specific cell over the course of your life, knocking out repair capacity in that cell completely.
When Both Copies Are Mutated
In rare cases, a child inherits a defective PALB2 gene from both parents. This causes a severe childhood condition called Fanconi anemia subtype N (FA-N). Children with this form of Fanconi anemia can have growth delays and congenital abnormalities, but the hallmark is an unusually aggressive predisposition to childhood cancers. All eight cases initially described in the medical literature developed cancer in early childhood, including brain tumors and kidney tumors. This is a fundamentally different situation from carrying a single mutation and is extremely rare.
Treatment Implications
Because PALB2-mutated cancers can’t repair DNA through homologous recombination, they have a specific vulnerability. A class of drugs called PARP inhibitors exploits this weakness by blocking a backup DNA repair pathway, effectively trapping cancer cells with no way to fix their DNA. The cells accumulate so much damage that they die.
Clinical evidence supports this approach. The Olaparib Expansion Trial (TBCRC 048) demonstrated that PARP inhibitors were effective in patients with metastatic breast cancer caused by PALB2 mutations. In one published case, a 39-year-old woman with metastatic breast cancer and a PALB2 mutation showed reduced tumor markers and favorable imaging after starting a PARP inhibitor. However, resistance can develop over time as tumors sometimes acquire new mutations that restore their DNA repair ability.
Platinum-based chemotherapy works on a similar principle, creating DNA damage that PALB2-deficient cancer cells struggle to repair. Both treatment strategies are borrowed from the BRCA playbook, since PALB2-mutated tumors share the same underlying repair deficiency. This connection has expanded the treatment options available to people whose cancers were historically grouped with more generic subtypes.
Getting Tested
PALB2 is included in most multi-gene panel tests ordered through genetic counselors or oncologists. Testing is typically recommended if you have a strong family history of breast or pancreatic cancer, particularly if BRCA1 and BRCA2 testing has already come back negative. About 5% to 10% of breast cancers are driven by inherited mutations, and PALB2 accounts for a meaningful share of those that aren’t explained by BRCA genes.
If you test positive, your blood relatives may also want to consider testing, since each first-degree relative has a 50% chance of carrying the same mutation. Knowing your status opens the door to enhanced screening (such as breast MRI starting at younger ages), risk-reducing strategies, and, if cancer does develop, targeted treatment options that wouldn’t otherwise be on the table.