A Study of the Possible Effects of Medication on Young Onset Colorectal Cancer (YOCRC)

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).