ICD-10 Code C18.6 – Malignant neoplasm of descending colon (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C18.6 – Malignant neoplasm of descending colon
What it is
C18.6 identifies a malignant tumor arising in the descending colon, the left-sided large bowel segment. Use it when documentation states primary cancer of the descending colon.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include colorectal mass, altered bowel habits, abdominal pain, anemia, or evidence of malignant disease on colonoscopy and pathology.
When to use this code
Use C18.6 when the provider documents primary malignant neoplasm of the descending colon, including biopsy-confirmed cancer or operative/pathology reports naming that site. It is also appropriate when the record clearly identifies the descending colon as the primary location. Check documentation if the site is described only as left colon or colon NOS.
Do not use for
Do not use this code for benign polyps, carcinoma in situ, or metastatic cancer to the colon from another primary site. If the documentation does not specify descending colon, check documentation.
Coding tip
Code the most specific documented colon site and confirm whether the malignancy is primary, secondary, or unspecified.