ICD-10 C20
Billable / Specific HCC v28: 11 CCMalignant neoplasm of rectum
About ICD-10-CM C20
ICD-10-CM code C20 represents Malignant neoplasm of rectum. This is a billable/specific code in the Neoplasms chapter (block C20). The 2026 edition of ICD-10-CM C20 became effective on October 1, 2025.
Coding Tips for C20
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
C20 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.
C20 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 C20. Per CMS ICD-10-CM Tabular 2026.
- Malignant neoplasm of rectal ampulla
Type 1 Excludes
Pure excludes, these codes can never be coded together with C20. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- malignant carcinoid tumor of the rectum (C7A.026)
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 rectum. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for C20
Local Coverage Determinations (LCDs) from CMS MACs that list C20 as a covered diagnosis.
Showing top 10 of 1,760 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing C20.
5 Medicare
CPT Codes Commonly Billed with C20
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 44408 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 45379 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44406 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 45390 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 45392 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44394 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44402 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44390 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44405 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
- 44388 CMS LCD: Billing and Coding: Diagnostic Colonoscopy CMS LCD
Convert C20 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 |
|---|---|---|
| C20 | 1541 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To C20
Other codes in section C15-C26 (Malignant neoplasms of digestive organs).
ICD-10 C20, Billing FAQ
Is ICD-10 code C20 billable? +
Yes, C20 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 C20? +
ICD-10 C20 includes: Malignant neoplasm of rectal ampulla.
What codes are Type 1 Excludes for C20? +
Type 1 Excludes (never code together with C20): malignant carcinoid tumor of the rectum (C7A.026)
Does C20 affect Medicare Advantage HCC risk adjustment? +
Yes. C20 maps to CMS-HCC v28 category 11. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is C20 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 C20? +
Procedures frequently paired with C20 include: 44408, 45379, 44406, 45390, 45392.
What ICD-9 codes does C20 map to? +
Per CMS GEMs, C20 maps to ICD-9 codes: 1541. 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 May 31, 2026.
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