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Cancer Genetics

Cancer is caused by genetic changes that lead to uncontrolled cell growth. While ALL cancer is genetic, most cancer is NOT inherited. Most of the time, these genetic changes occur during our lives due to random events.

Some families have a very strong history of cancer. In some of these families an inherited cancer predisposition gene is responsible for the cancer. The most common inherited cancers include breast, ovarian and colon cancer, although there are other less common cancers that are linked to a genetic predisposition.

The role of the Genetics team is to conduct a formal assessment of cancer risk, counseling and offer genetic testing if appropriate. Based on this consultation, screening recommendations are made.

Who we Help

Individuals who may have an inherited cancer predisposition gene.


Credit Valley Hospital site -  room 1A100
2200 Eglinton Ave. W.
Mississauga, Ontario L5M 2N1


Monday to Friday, 8:00 am – 5:00 pm

Contact Information

Phone: 905-813-4104
Fax: 905-813-4347


A referral from a doctor is required. For more information see What Information is Needed to Make a Referral? below

Resources for Patients & Their Families

What Information is Needed to Make a Referral?
Helpful information to give to your healthcare provider:

  • Relevant family history including:
    • who in the family has the condition(s)
    • how are they related to you
    • age of diagnosis
  • Medical records for the affected individual such as:
    • genetic test results
    • doctor’s consultation letters
    • pathology reports from surgery
    • test results, such as x-rays, ultrasounds, blood work

What Should I Consider in My Family History?

  1. The number of blood relatives on the same side of the family (mother’s or father’s) who have been diagnosed with cancer.
    Generally, if many relatives have had cancer, there is an increased chance genetics could be playing a role in the cause of the cancers. However, this is dependent on the size of the family. Smaller families may have fewer affected individuals.
  2. The age at cancer diagnosis.
    Generally, the younger the age at diagnosis, the greater the chance genetics could be playing a role.
  3. The type of cancer:
    Generally, if all the family members have the same type of cancer, there is an increased chance of a hereditary form of cancer. There are some different types of cancer well known to occur in the same person/family, such as colon and uterine cancer or breast and ovarian cancer.
  4. More than one cancer in the same person:
    Generally, if a person has had more than one cancer diagnosis, particularly in a different part of the body there is an increased chance of a hereditary form of cancer.

What Can I Expect During a Genetic Counselling Appointment?

Everyone who is referred to Genetics will have their case reviewed by a Geneticist and/or Genetic Counsellor before the appointment.
You will meet with a Genetic Counsellor. During the appointment your family history will be reviewed. Genetic counseling involves education about the genetic mechanisms related to cancer. The genetic counsellor will provide a cancer risk assessment based on medical and family history. Options for genetic testing and recommendations for preventive screening and treatments will be discussed.

If indicated, genetic testing is offered, but only after the benefits, risks and limits of each test are carefully explained. Choosing if and when to have genetic testing is ultimately a very personal decision. Genetic testing is most often done on a blood sample. Another appointment will be arranged to go over the results of your genetic testing.​