A family history is typically a part of a physician's examination. It is obtained through a series of questions that focus on health and social issues. It is especially important for people with a strong familial history of cancer.

According to the National Cancer Institute (NCI), indicators of inherited risk of cancer include the following:

• Clustering of the same type of cancer in close relatives (parents, siblings, children)
  
  
• Two or more primary cancers in one relative
  
  
• Onset of cancer at an earlier than usual age in one or more individuals
  
  
• Cancer in the sex not usually affected (e.g., breast cancer in men)
  
  
• Evidence of autosomal dominant inheritance 
  
  
• Bilaterality in paired organs (e.g., both lungs or both ovaries are affected)
  
  
• Patterns of cancer in the family that are associated with a known cancer syndrome or with other diseases

When hereditary cancer is suspected, the physician may have the patient collect information for a more detailed family history called a pedigree (also called a family tree). This chart of family relationships tracks patterns of the transmission of disease.

The NCI recommends the following if there appears to be a high family risk of cancer:

• A cancer family history that includes:
  
  
• Relatives on the mother’s side and the father’s side, including those without cancer
  
  
• Noting of nonpaternity, consanguinity (marrying among close blood relatives) and use of assisted reproductive technology such as donor egg or sperm
  
  
• Race, ancestry, and ethnicity information for all grandparents
  
  
• Seemingly unrelated conditions, such as birth defects
  
  
• Information of a minimum of three generations
  
  
• A three-generation family history that includes:
  
  
• First-degree relatives (parents, siblings, children)
  
  
• Second-degree relatives (grandparents, aunts and uncles, nieces and nephews, grandchildren)
  
  
• Third-degree relatives (cousins, great aunts, great uncles, great grandparents) who have had cancer or have had a first-degree relative afflicted with cancer
  
  
• Collecting the following information for any relative who has cancer:
  
  
• Type of each primary cancer
• Age of diagnosis for each primary cancer
• Where this person was diagnosed and treated
• Current age, or age at death and cause of death
• Exposure to carcinogens (such as smoking or radiation)
• Other significant health problems
  
  
• Collecting the following information for any relative who does not have cancer:
  
  
• Current age, or age at death and cause of death
  
  
• Any surgeries that reduce the risk for cancer
  
  
• Whether the person has had routine screening for cancer
  
  
• Any nonmalignant features of the syndrome in question
  
  
• Exposure to carcinogens
  
  
• Other significant health problems

This information may be used to help determine whether a family may have a hereditary cancer syndrome, what the most likely diagnosis is if a syndrome is indicated, and how the genetic traits are passed down in the family (dominant, recessive or X-linked). Answering these questions can help individuals make a more informed decision on whether to take precautionary measures and whether to undergo genetic tests and genetic counseling.

The information may also help a physician determine when a patient should undergo certain screening tests. For example, women at average risk for breast cancer should begin screening mammograms at age 40. If a woman has breast cancer in her family or is known to have a gene mutation associated with the disease, her physician may recommend that mammograms begin at an earlier age and with greater frequency.