ICD-10 Code C18.7 – Malignant neoplasm of sigmoid colon (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C18.7 – Malignant neoplasm of sigmoid colon
What it is
C18.7 identifies a malignant tumor arising in the sigmoid colon, the lower left segment of the large intestine. Use it when the record clearly documents primary cancer in that specific colon site.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include abdominal pain, altered bowel habits, rectal bleeding, anemia, weight loss, or an abnormal colonoscopy/biopsy confirming malignancy.
When to use this code
Use C18.7 when the provider documents primary malignant neoplasm of the sigmoid colon, including pathology-confirmed or clinically diagnosed cases. Code it from operative reports, oncology notes, or discharge summaries when the site is specified. If the record only says “colon cancer” without location, check documentation.
Do not use for
Do not use C18.7 for cancer in another colon segment, rectal cancer, or metastatic disease to the sigmoid colon from another primary site. Check documentation when the note is ambiguous.
Coding tip
Verify the exact anatomic site in pathology or provider documentation before assigning C18.7.