ICD-10 Code C78.5 – Secondary malignant neoplasm of large intestine and rectum (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C78.5 – Secondary malignant neoplasm of large intestine and rectum
What it is
This code identifies metastatic cancer that has spread to the large intestine or rectum from another primary site. Use it for secondary, not primary, colorectal malignancy.
Clinical signs
Clinical features vary; refer to documentation. Patients may have imaging, endoscopy, or pathology showing metastatic involvement of the colon or rectum, often in the setting of known cancer elsewhere.
When to use this code
Use C78.5 when the record clearly states secondary malignant neoplasm of the large intestine or rectum, or when pathology confirms metastatic disease in these sites. You may also use it when the provider documents spread from another primary malignancy to the colon or rectum. Check documentation if the primary site is unclear.
Do not use for
Do not use this code for primary colorectal cancer or for benign polyps, inflammatory disease, or nonspecific bowel masses. If the note only says “colon cancer” without secondary wording, verify the primary site.
Coding tip
Always code the primary malignancy first when documented, then assign C78.5 for the metastatic site.