Cohort 1. Li Fraumeni (TP53 mutations carriers)

Patients with a germline TP53 alteration included in this study will undergo their usual surveillance with their treating team. In addition to their routine scans or examinations, they will provide blood samples at enrollment, during the study (optional) and at the end of their participation (at 12 months). The results of any radiological scan undergone during this period will be collected retrospectively and added to their data collection, which will allow for a correlative analysis between the genetic and epigenetic results and radiological outcomes.

Cohort 2. Gastro-intestinal (GI) cohort

Patients with underlying germline conditions at high risk of developing a GI malignancy (approximately 40-50 patients)~* Lynch syndrome (MLH1, MSH2, MSH6, PMS2, EPCAM genes)~* PTEN~* STK11 (Peutz-Jeghers syndrome)~* CDH1 and APC gene alterations carriers prior to their risk-reducing surgery if such is performed.~* SMAD4~* MUTYH\* (\*biallelic variants)~Carriers of CDH1 and APC pathogenic mutation are invited to give blood and optional urine samples before and after their surgery, if they undergo this intervention, with no need for sequential samples. Samples should be taken when convenient for the patient prior to and post-surgery.