In cancer, cells grow and divide at an abnormally fast rate. Cancer may develop because of alterations to the cell’s genes. These changes may be hereditary or caused by environmental factors.

Usually, the body sends signals to tell cells when to stop dividing or die. If there are genetic changes to cells’ behavior, they ignore these signals and continue to reproduce. These cells may spread into the surrounding tissue and may cause tumors.

According to the American Cancer Society, cancer affects one-third of all people in the United States.

This article explores the relationship between genes and cancer and the types of cancer that have family links. It also looks at genetic testing and diagnosis.

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According to the National Cancer Institute (NCI), cancer is a genetic disease, meaning that changes to someone’s genes can lead to cancer. These changes can be hereditary, meaning that they run in families. Alternatively, the changes happen throughout someone’s life because of environmental factors or errors when cells divide.

Acquired mutations, or changes to the genes, are the most common cause of cancer. They are often caused by:

Germline mutations are hereditary cancers. The mutation happens in a sperm or egg cell, meaning that cells copy the change into each new cell. Inherited cancer makes up around 5–20% of all cancers.

Researchers have linked germline mutations with over 50 hereditary cancer syndromes. These syndromes may make someone more likely to develop certain types of cancer.

The following are some of the major types of cancer than can have genetic links:

Breast cancer

Breast cancer is the second most common cancer in women after skin cancer. According to the NCI, doctors diagnose around 12.9% of women with breast cancer at some point during their lifetimes.

Symptoms in women include:

  • swelling of the breast
  • breast or nipple pain
  • swollen lymph nodes
  • nipples turning inwards
  • discharge from the nipple
  • skin dimpling

Although breast cancer usually develops in women, men can also develop it. The American Cancer Society estimates that doctors will diagnose around 2,650 new breast cancer cases in men in the United States in 2021.

Symptoms in men may include:

  • a usually painless lump in the breast tissue
  • skin dimpling
  • retraction of the nipple
  • scaling or redness of the skin around the breast
  • discharge

Various factors impact breast cancer prognosis, including the stage at which doctors find and treat it. There is an overall 90% relative 5-year survival rate for females.

However, survival rates will depend on many factors. Also, since the research behind these statistics is from 5 years ago, the rates may have improved with advances in medical science.

Factors that may affect survival rates include:

  • age
  • overall health
  • disease involvement
  • tumor grade
  • response to treatment

Colorectal cancer

The overall relative 5-year survival rate for colon cancer is 63%.

For rectal cancer, the 5-year survival rate is 67%.

Prostate cancer

After skin cancer, prostate cancer is the most prevalent cancer in men. It is the second leading cause of cancer deaths among men in the United States after lung cancer.

Some of the symptoms of prostate cancer include:

  • blood in the urine
  • blood in the semen
  • erectile dysfunction
  • urination issues, such as a weak stream or increased frequency
  • weakness in the legs or feet
  • loss of bladder control
  • pain in the hips, spine, or ribs

The overall relative 5-year survival rate for prostate cancer is 98%.

Other genetic cancers

Other cancers that can be genetic include:

Various types of genes exist, but not all of them affect hereditary cancer syndrome. Here are some that can:

Oncogenes

Proto-oncogenes are genes that help cells grow. When the cell mutates or replicates too many times, it becomes an “oncogene.” These cells are in a constant state of activation, continually creating cells. This type of gene mutation is usually not hereditary but mostly acquired.

Tumor suppressor genes

These genes repair mistakes in DNA, slow down replicating cells, and send signals that tell a cell to die. When these break, they cannot correct errors, and cells do not die. The cells continue to divide and replicate long after they should have stopped, leading to tumor development.

Some of the most common hereditary cancer syndromes and the mutated genes experts associate with them are below.

SyndromeGenes
Hereditary Breast and Ovarian Cancer (HBOC)BRCA1, BRCA2
Lynch; also called “Hereditary Nonpolyposis Colorectal Cancer” (HNPCC)EPCAM, MLH1, MSH2, MSH6, PMS2
Li-FraumeniTP53
Hereditary Diffuse Gastric CancerCDH1
Peutz-JegherSTK11
Familial Atypical Mole/ Multiple Melanoma (FAMMM) + Pancreatic CancerCDKN2A (p16INK4a)
PTEN Hamartoma Tumor syndrome (PHTS)PTEN
Familial Adenomatous Polyposis; also associated with Gardner and Turcot syndromes.APC

The treatment for genetic cancers is the same as for other cancers. Depending on the type and stage of cancer, treatment options could include:

People should discuss treatment options with their healthcare providers to see which therapies are options for them.

Genetic testing can tell an individual if they have an increased risk of developing certain cancers. The test looks for gene mutations for cancers, including:

Not everyone with a genetic mutation will develop cancer. However, genetic testing means people can understand their risks and adjust their lifestyles accordingly.

With increased awareness, people may notice symptoms earlier and begin earlier treatment if cancer does develop.

Genetic counseling can help someone fully consider the risks, benefits, and limitations of genetic testing for their situation.

Genetic testing does not diagnose cancer. Instead, it shows that someone has a higher risk of developing cancer. A positive genetic testing result is not a guarantee that someone will develop cancer.

Before a healthy individual can seek genetic testing, it may be best for doctors to test a family member with cancer. The test looks to see if they carry a cancer risk gene that could be passed along.

If the person with cancer has a positive test, healthy family members can then undergo predictive genetic testing to see if they have the same gene.

People should discuss with their doctor whether genetic testing is right for them if they have a personal or family history of cancer. Factors that may suggest a hereditary link include cancer that was:

  • diagnosed at an unusually early age
  • in both organs in a pair, such as the lungs or kidneys
  • the same type of cancer in several first-degree relatives (parents, children, siblings)
  • unusual, such as breast cancer in a man

All cancers have a genetic link, either through hereditary genes or mutations caused throughout a person’s life.

It can be helpful for people with a family history of cancer to have genetic testing to find out if they are at higher risk of developing certain cancers.

People considering genetic testing should start with genetic counseling so they can carefully weigh the benefits and potential downsides.