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.

Microplastics in Paraneoplastic and Intratumoral for Colorectal Cancer