ICD-10 Code C18.4 – Malignant neoplasm of transverse colon (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C18.4 – Malignant neoplasm of transverse colon
What it is
This code identifies a malignant tumor arising in the transverse colon, the middle section of the large intestine. Use it when the documentation specifies cancer of the transverse colon.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include abdominal pain, altered bowel habits, anemia, weight loss, or evidence of a colon mass on imaging or colonoscopy.
When to use this code
Use C18.4 when the provider documents primary cancer of the transverse colon, including biopsy-confirmed or clinically diagnosed cases. It also applies when the record clearly localizes the malignancy to the transverse colon. Check documentation if the site is described only as colon cancer without a location.
Do not use for
Do not use this code for benign colon polyps, carcinoma in situ, or malignancy documented in another colon segment. If the primary site is uncertain or metastatic disease is described only, check documentation.
Coding tip
Code the site exactly as documented; transverse colon is not interchangeable with ascending, descending, sigmoid, or unspecified colon.