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Hereditary Diffuse Gastric Cancer (HDGC)

What is hereditary diffuse gastric cancer? 

Hereditary diffuse gastric cancer, or HDGC, is a type of rare cancer that grows in the stomach, which is the organ that helps digest food. HDGC usually grows in more than one area of the stomach, so it can be difficult to detect and treat. It can grow quickly and can spread to other parts of the body. 

This type of stomach cancer is caused by a genetic condition, which means parents can pass it on to their children. Having HDGC also increases the risk of getting other types of cancer, such as breast cancer.

How common is HDGC?

It is not known exactly how many people have HDGC. The frequency of HDGC also varies among different ethnicities. HDGC makes up only about 1% to 3% of all stomach cancer cases. Most patients with HDGC are diagnosed before the age of 40.

How is HDGC diagnosed?

People with family members with HDGC can receive genetic testing to see if they have a mutation in the CDH1 gene, or other rarer mutations that are known to cause HDGC. Genetic counseling is recommended for people with two or more immediate family members diagnosed with diffuse gastric cancer or diagnosed with gastric cancer at a young age. Different types of CDH1 mutations are associated with certain risks, like developing cancer at a young age. To see if this information changes the management of your cancer and family members who may be at risk, please talk with your genetic counselor and doctor.

HDGC can be hard to diagnose because some of the more common imaging tests used to search for cancer in the stomach cannot pick up HDGC. This leads to HDGC being diagnosed at later stages when the cancer is more advanced. Symptoms can include:
•    Stomach pain
•    Nausea and vomiting 
•    Loss of appetite 
•    Weight loss
•    Trouble swallowing

When HDGC has spread to other parts of the body, imaging tests and biopsies may be done to diagnose HDGC. 

Imaging: If you have symptoms of HDGC, your doctor will use imaging scans such as ultrasound, CT, and PET to look at where the tumor is and how big it is. They will also check for signs that the tumor has spread to other parts of the body.

Biopsy: To check if the tumor is HDGC your doctor will do one or multiple biopsies, taking a small sample from the tumor with a needle. An expert, called a pathologist, will study cells from the sample under the microscope to see what kind of tumor it is.

How is HDGC treated?

Treatment for each patient will be unique. You should go to an expert in HDGC treatment to decide the best approach for your tumor. You can contact MyPART for help finding experts near you.

Surgery: Surgery is most commonly used to remove the stomach to reduce the risk of developing cancer.  Usually, the entire stomach is removed to prevent the cancer from growing and spreading. 

Chemotherapy:  When surgery is not possible or when the cancer has spread, chemotherapy is used to treat HDGC.

Does HDGC run in families?

Yes, HDGC runs in families. Parents with a mutation in the CDH1 gene that causes HDGC have a 50% chance of passing on the mutation to their children.

How does HDGC form?

Because HDGC runs in families, we know that changes in the CDH1 gene are important in causing some cases of HDGC. But not all people with HDGC have a mutation in CDH1, so scientists are studying what causes HDGC to form. The time it takes for HDGC to form in patients and their family members can be very different. 

What is the prognosis for someone with HDGC?

The estimate of how a disease will affect you long-term is called prognosis. Every person is different and prognosis will depend on many factors, such as: 

•    Where the tumor is in your body
•    If the cancer has spread to other parts of your body
•    How much of the tumor was taken out during surgery 

If you want information on your prognosis, it is important to talk to your doctor. Also, NCI has resources to help you understand cancer prognosis

When HDGC is found when it is small, the survival rate is high. When HDGC is already large or has spread to other parts of the body, treatment is more difficult and the five-year survival rate is less than 20%. People with a mutated CDH1 gene have the option of having surgery to remove their stomach before developing HDGC to prevent getting cancer. This can cause life-long symptoms related to eating and digestion and should be discussed with your doctor and nutritionist.