Microplastics in Paraneoplastic and Intratumoral for Colorectal Cancer

Inclusion Criteria: * Adult patients (≥18 years old) with histologically confirmed colorectal adenocarcinoma. * Undergoing elective radical colorectal cancer resection at the study hospital. * No prior chemotherapy, radiotherapy, or targeted therapy before surgery. * Availability of both tumor tissue and adjacent normal (peritumoral) tissue samples during surgery. * Willingness to provide stool and/or blood samples for metagenomic and metabolomic analysis. * Ability to understand the study procedures and provide written informed consent. Exclusion Criteria: * Patients with a history of other malignancies within the past 5 years. * Emergency surgery due to obstruction, perforation, or bleeding. * Inadequate sample quality or volume for microplastic, metagenomic, or metabolomic analysis. * Presence of chronic inflammatory bowel disease (e.g., Crohn's disease or ulcerative colitis). * Use of antibiotics, probiotics, or prebiotics within 4 weeks prior to sample collection. * Pregnant or breastfeeding women. * Refusal or inability to provide informed consent.