Inclusion Criteria:

- colorectal cancer (CRC) in two first degree relatives, one being diagnosed before 61
years of age

- CRC diagnosed before 51 years of age or advanced colorectal adenoma before 41 years
of age

- multiple primary CRCs in the same individual, the first being diagnosed before 61
years of age.

Exclusion Criteria:

- Lynch syndrome,

- adenomatous polyposis defined by more than 10 adenomas histologically proved,

- hamartomatous polyposis defined by one hamartoma histologically proved,

- absence of informed consent.