Carcinoma in situ of colon

This code represents the presence of abnormal, cancerous cells that are confined to the innermost layer of the colon wall and have not invaded deeper tissues. It signifies a pre-invasive stage of colorectal cancer, often detected during screening colonoscopies.

Use this code when pathology reports confirm carcinoma in situ of any part of the colon, excluding the rectosigmoid junction. Documentation should clearly state "carcinoma in situ" or "intramucosal carcinoma" of the colon.

• Do not use this code if the lesion has invaded beyond the muscularis mucosae; in such cases, a malignant neoplasm code would be appropriate.
• Carefully review the pathology report to differentiate between carcinoma in situ of the colon and the rectosigmoid junction.
• This code is often used as a primary diagnosis when the carcinoma in situ is the reason for the encounter (e.g., for removal or surveillance).