STK11 Gene Mutations (Peutz-Jeghers Syndrome)

What is STK11 and Peutz-Jeghers syndrome?

STK11 is a gene that helps repair damage to your DNA. People who are born with changes—called mutations—in the STK11 gene have a syndrome known as Peutz-Jeghers syndrome and an increased risk for several types of cancer.   

Does everyone with Peutz-Jeghers syndrome develop cancer?

The lifetime risk for cancer with an STK11 mutation is high, and many people with an inherited mutation in the STK11 gene will develop cancer in their lifetime. Following the guidelines for screening and prevention increases the chances of preventing cancer or catching it at its earliest and most treatable stage.

My tumor has a STK11 mutation. Does that mean I have Peutz-Jeghers syndrome?

No, testing positive for a STK11 mutation in your tumor does not necessarily mean you have Peutz-Jeghers syndrome. However, if you have a tumor STK11 mutation, you should speak with your doctor about genetic counseling and testing.  

STK11 mutations in tumors

Tumor testing (also known as biomarker testing) can look for different mutations within a cancer cell. Doctors order these tumor tests to make decisions about the best way to treat the cancer. Unlike normal cells, cancer cells often have many different types of mutations. Mutations that are only found within cancer cells are called acquired (somatic) mutations. Somatic STK11 mutations are uncommon in most cancers, but may be more common in  a certain type of lung cancer known as non-small cell lung cancer (NSCLC). People with somatic STK11 mutations in their cancer cells do not develop Peutz-Jeghers syndrome.  

Germline STK11 mutations

Most people who are born with STK11 mutations inherited the mutation from one of their parents. These people will have the mutation in every cell in their body. Mutations that are  inherited are called germline mutations. People with germline STK11 mutations have Peutz-Jeghers syndrome. Genetic testing is used to test people for an inherited mutation in STK11 and Peutz-Jeghers syndrome. 

De Novo STK11 mutations

Some people with Peutz-Jeghers syndrome are the first in their family to develop the condition. These people did not inherit their STK11 mutation from either parent. This is known as a de novo mutation. De novo mutations happen to a person during development in the womb before they are born. People with de novo STK11 mutations may develop Peutz-Jeghers cancers, but depending on when the mutation happened during development, they may or may not have the mutation in every cell in their body. If the mutation is in their egg or sperm, they can pass the mutation on to their children. 

How do I find out if I have Peutz-Jeghers syndrome?

Genetic testing is a type of medical test that can help people learn if they have an inherited mutation in STK11 and other genes. The test can be performed on blood, saliva or tissue. The sample is collected and sent to a genetic testing lab. 

It's a good idea to speak with a genetics expert before having genetic testing. They will answer your questions about testing and ensure that the correct test is ordered. 

What are the cancer risks for people with an STK11 mutation?

People with an inherited mutation in STK11 have a very high lifetime risk for different types of cancers, including:

• breast cancer
• colorectal cancer
• endometrial cancer
• lung cancer
• pancreatic cancer
• stomach cancer
• small intestinal cancer
• other cancers

The risks for cancer begin at a young age.

What can people do if they have Peutz-Jeghers syndrome?

If you test positive for an STK11 mutation, you have options. There are expert guidelines and clinical trials that focus on:

• cancer risks
• screening, early detection and risk-reduction

These guidelines are based on the most current research and updated yearly. People who test positive for an STK11 mutation should speak with a genetics expert to make sure that their medical care is based on the most up-to-date information. 

If you test positive for an STK11 mutation, you should inform your close blood relatives (first-, second-, and third-degree relatives) about your test results and encourage them to speak with a genetics expert.