This study will collect biospecimens (including blood, tissue, and stool samples) and health information to create a database-a type of collection of information-for better understanding young onset colorectal cancer (YOCRC). The study will include both people with YOCRC and healthy people.

Inclusion Criteria:

CRC Cohort:

• 18-49 years old
• Histological or cytological diagnosis of colorectal adenocarcinoma
• Planned CRC resection biopsy, or colonoscopy ,including surveillance colonoscopies and/or have already undergone prior surgical resection, with tissue, including normal colonic mucosae distant from the malignant tumor (only patients providing tissue sample)
• Enrollment in IRB# 20-315, Young Onset Gastrointestinal Cancer Prospective Registry (Andrea Cercek, PI)

Healthy Control Cohort:

• 18-49 years old at time of diagnosis
• Scheduled for standard-of-care colonoscopy at MSK
• Underwent surgical resection of a traumatic injury to the colon at Shaare Zedek Medical Center (SZMC)

Exclusion Criteria:

• CRC Cohort:
• Antibiotic use within 6 months of collection of stool for gut microbiome analysis s (only patients providing stool sample)
• Known inherited cancer susceptibility gene
• History of inflammatory bowel disease

Healthy Control Cohort:

• Antibiotic use within 6 months of collection of stool for gut microbiome analysis (only patients providing stool sample)
• History of or prior treatment for cancer ≤ 5 years prior to registration. Exceptions include non-melanoma skin cancer, ductal carcinoma in situ, bladder carcinoma in situ, or carcinoma-in-situ of the cervix.
• Colonoscopy for indications of IBD, anemia and/or genetic predisposition (only patients providing tissue sample).

Potential research subjects will be identified through the Center for Young Onset Colorectal and Gastrointestinal Cancer, a member of the patient's treatment team, the principal and coprincipal investigator, or research team at Memorial Sloan Kettering Cancer Center (MSKCC).

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.