The goal of this observational study is to see whether a new, noninvasive test that analyzes smells (odor) from breath and intestinal gas can help detect colorectal cancer and precancerous growths at an early stage.

The main questions it aims to answer are:

Can the new odor-based test correctly identify people who have colorectal cancer or precancerous lesions?

How accurate is the new test compared to the current standard method (colonoscopy with biopsy)?

Researchers will compare the results of the new test with standard diagnostic results.

Participants will be asked to:

Provide samples of breath, urine, stool, and intestinal gas (collected using a special device or a collection bag)

Allow researchers to review their medical records and colonoscopy results

Answer questions about their health history and lifestyle

This study involves no treatments or procedures beyond normal medical care. It only collects samples and data for research purposes.

Inclusion Criteria:

• Age 18 to 85 years, male or female
• Histopathologically or cytologically confirmed colon or rectal cancer (TNM stage I-IV) for colorectal cancer group
• Histopathologically confirmed adenomatous polyps, sessile serrated lesions, traditional serrated adenomas, or other precancerous lesions for precancerous lesion group
• No abnormality on colonoscopy within the past year; no personal history of colorectal cancer or other malignancies; no chronic diseases requiring long-term treatment for healthy control group
• Willing and able to provide signed informed consent

Exclusion Criteria:

• Hereditary colorectal cancer syndromes (e.g., familial adenomatous polyposis, hereditary non-polyposis colorectal cancer)
• Autoimmune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis)
• Severe cardiovascular, respiratory, or urinary system diseases
• Other primary malignant tumors
• Hematological diseases
• Unable to comply with study procedures (e.g., sample collection or questionnaires)
• Planning to become pregnant, pregnant, or breastfeeding
• Suspected or confirmed alcohol or drug abuse
• Known allergy to any drug used for colorectal cancer treatment
• Participation in another interventional drug clinical trial within the past month
• Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study

The study population will consist of three groups recruited primarily from Beijing University of Chinese Medicine, Dongfang Hospital：

Patients with histopathologically confirmed colorectal cancer (TNM stage I-IV).

Patients with histopathologically confirmed precancerous lesions (e.g., colorectal adenomas, sessile serrated lesions).

Healthy controls with no abnormalities on colonoscopy within the past year and no history of colorectal cancer or other malignancies.

Participants will be adults aged 18 to 85 years. Healthy controls will be recruited from the same hospital settings and matched for key demographic factors (age, sex, BMI) and lifestyle habits to minimize confounding.