ICD-10 C18.9
Billable / Specific HCC v28: 11 CCMalignant neoplasm of colon, unspecified
About ICD-10-CM C18.9
ICD-10-CM code C18.9 represents Malignant neoplasm of colon, unspecified. This is a billable/specific code in the Neoplasms chapter (block C18). The 2026 edition of ICD-10-CM C18.9 became effective on October 1, 2025.
Coding Tips for C18.9
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
C18.9 is a CMS-HCC v28 risk-adjustment code (category 11). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
C18.9 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under C18.9. Per CMS ICD-10-CM Tabular 2026.
- Malignant neoplasm of large intestine NOS
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Inpatient DRG Impact, CC
codes Malignant neoplasm of colon, unspecified. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for C18.9
Local Coverage Determinations (LCDs) from CMS MACs that list C18.9 as a covered diagnosis.
Showing top 10 of 1,347 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing C18.9.
5 Medicare
CPT Codes Commonly Billed with C18.9
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 74177 CT abdomen/pelvis with contrast — abdominal pain, colon cancer staging, liver mets, cholelithiasis, pancreatitis, chronic pancreatitis, pancreatic cancer, hepatomegaly, splenomegaly, abnormal imaging Radiology
- 74176 CT abdomen/pelvis without contrast — same indications as with contrast when contrast contraindicated Radiology
- 81210 CMS LCD: Billing and Coding: MolDX: FDA-Approved BRAF Tests CMS LCD
- 81540 CMS LCD: Billing and Coding: MolDX: bioTheranostics Cancer TYPE ID� Update CMS LCD
- 45341 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
- 45331 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
- 45337 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
- 45332 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
- 45334 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
- 45335 CMS LCD: Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic CMS LCD
Convert C18.9 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| C18.9 | 1539 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To C18.9
Other codes in section C15-C26 (Malignant neoplasms of digestive organs).
ICD-10 C18.9, Billing FAQ
Is ICD-10 code C18.9 billable? +
Yes, C18.9 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to C18.9? +
ICD-10 C18.9 includes: Malignant neoplasm of large intestine NOS.
Does C18.9 affect Medicare Advantage HCC risk adjustment? +
Yes. C18.9 maps to CMS-HCC v28 category 11. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is C18.9 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with C18.9? +
Procedures frequently paired with C18.9 include: 74177, 74176, 81210, 81540, 45341.
What ICD-9 codes does C18.9 map to? +
Per CMS GEMs, C18.9 maps to ICD-9 codes: 1539. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on June 2, 2026.
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