Family cancer syndromes
Some conditions are linked to an increased risk of cancer because of an inherited gene mutation. These conditions are called family cancer syndromes or inherited (hereditary) cancer syndromes. Most family cancer syndromes are rare. Family cancer syndromes can lead to cancer in both children and adults, but it usually affects people at a younger age than normal.
Not everyone with an inherited cancer syndrome develops cancer. But people who know they have a family cancer syndrome and have a higher risk of developing cancer may choose to be screened for certain types of cancer or have preventive treatment, such as prophylactic surgery.
Who’s at risk?
Anyone who is concerned about having an inherited cancer syndrome in their family should talk to their doctor to see if they should meet with a genetic counsellor. Genetic counsellors see patients and their families who are suspected of having a family cancer syndrome and can help determine who is at risk and who should have testing. They also arrange the testing if it’s recommended.
There are more than 30 family cancer syndromes caused by mutations in different genes but these syndromes are rare. They may be suspected:
- in families who seem to have cancer more often than would be expected by chance
- when the cancer happens at a young age
- when certain subtypes of cancer are found
- when there is a clustering of certain cancers (cases of breast, ovarian and prostate cancer in a family)
- when a person has been diagnosed with more than one type of cancer
People from certain ancestries, such as Ashkenazi Jewish ancestry, also have higher rates of family cancer syndromes.
How are family cancer syndromes inherited?
Most family cancer syndromes are inherited in what is called an autosomal dominant pattern. We all have 2 copies of every gene – 1 from our mother and 1 from our father. For conditions with autosomal dominant inheritance, having a mutation in 1 copy of the gene is enough to increase a person’s risk of developing cancer. In this case, the risk that their children will have the syndrome is 50% (1 out of 2). But some family cancer syndromes are inherited in an autosomal recessive pattern. This means a person needs to have a mutation in both copies of the gene to increase their risk of cancer. In this case, both parents need to pass the mutated gene to a child.
There are also some family cancer syndromes that develop because of a gene mutation on the X sex chromosome (the chromosomes that determine a person’s sex). This is called an X-linked inherited pattern.
Some examples of family cancer syndromes are listed below.
Ataxia-telangiectasia affects the nervous system, immune system and other body systems. It can cause a loss of balance, poor coordination (ataxia), frequent infections, red eyes (due to widening of blood vessels) and abnormal eye movements. Ataxia-telangiectasia increases the risk of leukemia, lymphoma and breast cancer. It is caused by a mutation of the ATM gene, which normally repairs damage to DNA.
Unlike most types of family cancer syndromes, this is inherited in an autosomal recessive pattern. This means a mutation in both copies of a gene is needed to develop the condition. But those with only one mutation (called carriers) have an increased risk of breast cancer.
Basal cell nevus syndrome
Basal cell nevus syndrome is also called Gorlin syndrome or nevoid basal cell carcinoma syndrome. It is usually caused by a mutation in PTCH1, a tumour suppressor gene. This syndrome causes different problems with the skin, eyes, nervous system, endocrine glands and jawbone. People may also have a larger head size than average (called macrocephaly). Basal cell nevus syndrome increases the risk of non-melanoma skin cancer, brain and spinal cord cancer and soft tissue sarcoma.
Beckwith-Wiedemann syndrome causes the body to grow more than it should or unevenly (asymmetrically) during development and into childhood. Newborns may have hypoglycemia (low blood sugar). Children with Beckwith-Wiedemann syndrome have an increased risk of developing Wilms tumour (a type of kidney cancer that affects children), hepatoblastoma (a rare type of liver cancer that affects children), neuroblastoma, rhabdomyosarcoma and adrenal gland cancer.
Bloom syndrome is caused by a BLM gene mutation that changes the way chromosomes interact with each other. People with Bloom syndrome are usually smaller than average, have a high-pitched voice and easily develop skin rashes (especially over the nose and cheeks) after being in the sun. Having Bloom syndrome increases the risk of acute leukemia, lymphoma, breast cancer, colon cancer, bone cancer and Wilms tumour.
Carney complex causes changes in the colour of the skin, blue moles (nevi) and growth of a specific type of tumour called a myxoma in the skin, breast or heart. It increases the risk of endocrine gland tumours like thyroid and adrenal gland cancers and nerve sheath tumours. Carney complex is caused by a mutation in the PRKAR1A gene.
Cowden syndrome causes many non-cancerous tumour-like nodules, or lumps (called hamartomas), to develop in the skin, breast, thyroid, colon, small intestine and mouth. Cowden syndrome is caused by a mutation in the PTEN tumour suppressor gene. It increases the risk of breast, thyroid, uterine, colorectal and brain cancers. When the PTEN gene is mutated in certain types of brain cancer, the condition may also be called Lhermitte-Duclos syndrome.
Familial adenomatous polyposis (FAP)
Colon cancer is common and happens in about 6% of the general population. About 1% of colon cancers are caused by an inherited cancer syndrome called familial adenomatous polyposis (FAP). FAP is usually caused by a mutation of the APC gene. FAP causes hundreds to thousands of adenomatous polyps to develop on the inner lining, or mucosa, of the colon, rectum, small intestine and stomach. People with FAP may also have abnormal teeth, jaw cysts and tumours that start in muscle called desmoid tumours. FAP is highly linked to colorectal cancer and small intestine cancer. It also increases the risk of stomach, adrenal gland and thyroid cancers. People with FAP who don’t have treatment will almost always develop cancer.
Another gene linked to FAP is called the MYH gene. Two copies of this gene mutation (an autosomal recessive pattern) are needed to increase the risk of cancer.
Familial atypical multiple mole melanoma (FAMMM) syndrome
People with familial atypical multiple mole melanoma (FAMMM) syndrome have many moles (50 more moles than the average person). FAMMM is caused by a mutation in one of several genes including the p16 tumour suppressor gene. People with FAMMM have a very high risk of developing melanoma, a type of skin cancer. FAMMM also increases the risk of melanoma of the eye (a type of eye cancer) and pancreatic cancer. FAMMM is also called dysplastic nevus syndrome.
Gardner syndrome is related to familial adenomatous polyposis (FAP). People with Gardner syndrome develop many polyps in the colon but also have tumours outside of the colon. Like FAP, Gardner syndrome is caused by a mutation in the APC gene. People with Gardner syndrome have an increased risk of colorectal cancer, soft tissue sarcoma and thyroid cancers.
Hereditary breast and ovarian cancer (HBOC) syndrome
Breast cancer is common. It happens in 1 out of every 8 women. But only about 5% to 10% of women develop breast cancer because of an inherited cancer syndrome called hereditary breast and ovarian cancer (HBOC) syndrome. The syndrome is caused by a mutation in one of several genes. In about half of people with HBOC, the mutated genes are BRCA1 or BRCA2. HBOC increases the risk of breast, ovarian, prostate, fallopian tube and pancreatic cancers. People of Ashkenazi Jewish ancestry have about a 2.5% chance (about 1 out of 40) of having a mutated BRCA gene. This is much higher than in the general population.
Retinoblastoma is a type of eye cancer that affects children. Hereditary retinoblastoma is caused by an inherited RB1 gene mutation or an RB1 gene mutation that happens in the egg or sperm before conception and is passed on to the child. Children with hereditary retinoblastoma will usually develop retinoblastoma in both eyes and also have an increased risk of developing bone cancer, soft tissue sarcoma and melanoma later in life.
Li-Fraumeni syndrome is caused by a mutation in the p53 (Tp53) tumour suppressor gene or a mutation in the CHEK2 tumour suppressor gene. Normally, these genes help to prevent cancer by stopping cells from growing and dividing too quickly.
Li-Fraumeni syndrome increases the risk of several different types of cancer, including soft tissue sarcoma, osteosarcoma (a type of bone cancer), leukemia, brain cancer, adrenal cancer and breast cancer. These cancers tend to happen most often during childhood, except for breast cancer, which happens in young adults or later. And people with Li-Fraumeni syndrome can develop more than one type of cancer during their lifetime. They also tend to be more likely to develop a second cancer after having radiation therapy, so doctors try to avoid this treatment when they can.
About 2% to 3% of colorectal cancers are caused by Lynch syndrome. People with Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) have a mutation in 1 out of 4 genes that normally correct mistakes when DNA is copied during cell division. These genes are called DNA mismatch repair (MMR) genes.
People with Lynch syndrome have a high risk of colorectal cancer. When colorectal cancer develops in people with Lynch syndrome, it usually happens before age 50. Lynch syndrome also increases the risk of endometrial cancer (a type of uterine cancer) as well as pancreatic, ovarian, stomach and small intestine cancers.
Multiple endocrine neoplasia (MEN)
Multiple endocrine neoplasia (MEN) affects the endocrine system. People with MEN often develop tumours in more than one endocrine gland. There are 2 types of MEN. MEN type 1 (MEN1) is caused by a MEN1 gene mutation and is linked to adrenal gland cancer, islet cell pancreatic cancer, parathyroid gland cancer and pituitary gland cancer. The first sign of MEN1 is often high levels of parathyroid hormone in the blood due to cancer in one or more of the parathyroid glands. MEN type 2 (MEN2) is caused by a RET gene mutation and is linked to thyroid gland and parathyroid gland cancers and a type of adrenal gland cancer called a pheochromocytoma. Some people with MEN2 may be unusually tall and have enlarged lips.
Neurofibromatosis type 1
Neurofibromatosis type 1 is caused by a mutation in the NF1 gene. People with neurofibromatosis type 1 have patches of skin that have a different colour from the rest. The patches of skin are called café-au-lait spots that can be smooth or raised and from beige to dark brown. On lighter skin, the spots are the colour of coffee with lots of cream. On darker skin, they can be the colour of rich black coffee.
People with neurofibromatosis type 1 also develop tumours (called neurofibromas) along the nerves. Most tumours are non-cancerous but some can become cancerous over time. Neurofibromatosis type 1 increases the risk of several types of cancer including brain cancer, adrenal gland cancer, rhabdomyosarcoma, neuroblastoma, neuroendocrine tumours, soft tissue sarcoma and leukemia.
Peutz-Jeghers syndrome is caused by a mutation in the STK11 (also called LKB1) tumour suppressor gene and causes a very large number of polyps to develop in the gastrointestinal tract. It also causes dark spots on the lips, inside the mouth and on other mucous membranes. Peutz-Jeghers syndrome increases the risk of colorectal, stomach, pancreatic, small intestine and breast cancers. It also increases the risk of getting a blockage in the intestines (called a bowel obstruction).
Turcot syndrome is related to Lynch syndrome and familial adenomatous polyposis (FAP). People with Turcot syndrome develop many polyps in the colon. Turcot syndrome is caused by a mutation in the APC, MLH1 or PMS2 gene. It increases the risk of colorectal cancer and brain cancer.
Von Hippel-Lindau (VHL) syndrome
Von Hippel-Lindau (VHL) syndrome is caused by a mutation in the VHL tumour suppressor gene. People with VHL syndrome develop tumours and cysts in different parts of the body. These tumours are called hemangioblastomas and are made of abnormal blood vessels. Hemangioblastomas can happen in the back of the eye (retina), brain, spine and other organs. These tumours are non-cancerous but VHL increases the risk of kidney cancer, brain cancer, a type of adrenal gland cancer called pheochromocytoma and islet cell pancreatic cancer.
Werner syndrome causes premature aging that begins during the teenage years. It is caused by a mutation in the WRN gene. People with Werner syndrome have an increased risk of developing bone cancer, melanoma, soft tissue sarcoma and thyroid cancer.
Wiskott-Aldrich syndrome affects blood cells and cells of the immune system. People with Wiskott-Aldrich syndrome have lower numbers of platelets, which can cause them to bruise and bleed easily. They also have a higher risk for infection because their immune cells (such as T cells and B cells) don’t work properly. Wiskott-Aldrich syndrome increases the risk of leukemia and lymphoma and is caused by mutations in the WAS gene.
Xeroderma pigmentosum (XP)
Xeroderma pigmentosum (XP) affects the skin so it can’t repair sun damage as well as usual. When someone has XP, their skin is more sensitive to ultraviolet radiation from the sun. People with XP have a high risk of developing melanoma and non-melanoma skin cancers. XP is linked to mutations in several genes including the XPC, ERCC2 and POLH genes.
More information on hereditary and genetic conditions
The molecules inside the cell that program genetic information. DNA determines the structure, function and behaviour of a cell.
A gene normally found in the body that helps control cell growth and may help limit the growth of cancer cells.
When a tumour suppressor gene mutates (changes), or its gene expression is abnormal, cancer may develop.
Also called anti-oncogene.
A type of gland without a duct that releases hormones directly into the blood.
Examples of endocrine glands include the thyroid, parathyroid gland, pituitary gland, pancreatic islet cells, adrenal gland, pineal gland and the ovaries and testicles.
Also called ductless gland.
A specialized cell in the pancreas that produces insulin and other hormones that help control the level of sugar (glucose) in the blood.
Also called endocrine pancreas cell or islet of Langerhans cell.
The thin, moist layer of tissue that lines some organs and body cavities, including the nose, mouth, lungs, airways, vagina and gastrointestinal (GI) tract.
Glands in the mucous membrane make mucus (a thick, slippery fluid).
Also called mucosa.
Cancer affects all Canadians
Nearly 1 in 2 Canadians is expected to be diagnosed with cancer in their lifetime.