Allied Health Professionals

When do adenomas develop?


Adenomas are not present at birth. Adenomas generally begin around puberty, that is, from the age of 10-12. This is very different from the more common history of a 50- or 60-year-old person who may develop one or two adenomas. Most people with FAP are diagnosed in their teens or early 20's. It is estimated that only 1 per cent of all bowel cancer is due to FAP.

Two things may happen to adenomas over time: they increase in size and number. Adenomas form initially in the rectum and lower colon. Some people have hundreds or thousands of adenomas while others, particularly adolescents, may have fewer adenomas. One hundred polyps is the average number of polyps in a person with FAP but this depends on how old he or she is. This can be an important clue to treatment. Without early diagnosis and treatment, the risk of colon cancer is 100 per cent. FAP is a pre-cancerous disease because:

1. adenomas will change to cancer in approximately 5 to 10 years; and
2. prevention of colon cancer is possible.

There is a form of FAP called attenuated which may develop much later, up to 15 or more years, than classical FAP. However, there is no pattern as to the age when adenomas develop. Sometimes, an affected young adult may actually be diagnosed before the parent. The difference lies in a lower number of adenomas which occur higher up in the ascending colon or cecum. The risk of colon cancer is similar to classical FAP.

Adenomas in a segmented colon