How does the disease appear?

Hereditary bowel and rectum cancer syndromes can either be polyposis – when associated with multiple polyps –or nonpolyposis when none, or just a few polyps are present. 

Hereditary Non-Polyposis Colorectal Cancer (HNPCC) or Lynch Syndrome is, like the name indicates, nonpolyposis, but also the most common colorectal cancer syndrome.
Familial Adenomatous Polyposis (FAP) , on the other hand, is the most frequent of the polyposis syndromes.

LEARN MORE ABOUT THESE TWO SYNDROMES

The patterns how these syndromes manifest themselves in a family is very different, both, however, tend to appear in every single generation. 

This means, and especially with Lynch Syndrome, that if none of your parents had colorectal cancer, the chance that you will have a hereditary form of the disease is minimal. 

Additionally, there are other more rare polyposis syndromes , for example, MUTYH-associated polyposis (MAP). MUTYH is a gene involved in DNA repair.