Colorectal Cancer ICD-10-CM codes

Colon cancer is coded by segment with the fourth character of C18: C18.0 cecum, C18.1 appendix, C18.2 ascending colon, C18.3 hepatic flexure, C18.4 transverse colon, C18.5 splenic flexure, C18.6 descending colon, C18.7 sigmoid colon, C18.8 overlapping sites, and C18.9 colon unspecified. Cancer of the rectosigmoid junction is C19, rectum is C20, and anus and anal canal are C21.0 to C21.8. Colonoscopy and pathology reports almost always name the segment, so C18.9 should be uncommon.

Liver is the most frequent site of spread; code C78.7 in addition to the primary. Metastasis to regional lymph nodes is C77.2 (intra-abdominal) or C77.5 (intrapelvic). Sequencing follows the focus of care: the primary is first when it is being treated, the secondary site is first when treatment is directed only at the metastasis.

Benign polyps are not coded to chapter 2 malignancy categories: K63.5 is a polyp of colon and D12.- is a benign neoplasm (adenoma) by segment, with D12.6 for the colon unspecified. A polyp with high-grade dysplasia or carcinoma in situ is D01.- . Z86.0100 and Z86.0101 record a personal history of colon polyps (unspecified, or adenomatous and serrated) and support surveillance colonoscopy.

After curative resection with no evidence of disease and no ongoing treatment, report Z85.038 (history of malignant neoplasm of large intestine) or Z85.048 (rectum, rectosigmoid junction, and anus), plus Z90.49 if a portion of the bowel is absent. Z12.11 is the screening colonoscopy code for an average-risk patient; Z15.060 reports a confirmed genetic susceptibility such as Lynch syndrome.