C18.9 Malignant neoplasm of colon, unspecified

The ICD-10-CM code for Malignant neoplasm of colon, unspecified is C18.9 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

2: Neoplasms (C00-D49)

Section

C15-C26: Malignant neoplasms of digestive organs (C15-C26)

Category C18

11 codes (10 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to C18.9:

• Polyposis › coli › adenocarcinoma in
• Polyposis › coli › carcinoma in
• Adenocarcinoma › in › adenomatous › polyposis coli
• Carcinoma (malignant) › in › adenomatous › polyposis coli

Inclusion Terms

• Malignant neoplasm of large intestine NOS

U.S. Hospital Utilization

• An estimated 59,420 U.S. inpatient stays in 2023 included C18.9 among the documented diagnoses.
• 9,315 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Prevalence & Statistics

• In 2023, an estimated 1,478,528 people in the United States were living with colorectal cancer. (NCI SEER Cancer Stat Facts: Colorectal Cancer, 2023)

Official Coding Guidelines

Tx of primary site (TOC entry)

a. Admission/Encounter for treatment of primary site ............................................................. 33

Tx of secondary site (TOC entry)

b. Admission/Encounter for treatment of secondary site .......................................................... 33

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)
• NCI SEER Cancer Stat Facts: Colorectal Cancer (2023)