C19 ICD-10-CM Code: Malignant neoplasm of rectosigmoid junction
C19 maps to CMS-HCC V28 22. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)
C19
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of rectosigmoid junction
Cancer that occurs at the rectosigmoid junction, which is the area where the sigmoid colon meets the rectum.
Buddy Insight
Malignant neoplasm of the rectosigmoid junction is clinically significant because tumors at this boundary zone between the sigmoid colon and rectum may require treatment approaches from both colon and rectal cancer paradigms.
CMS-HCC V28
MappedHCC 22
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 011
Code-level coefficient reference
ESRD/PACE
MappedHCC 11
Code-level coefficient reference
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Malignant neoplasm of colon with rectum
- Malignant neoplasm of rectosigmoid (colon)
Excludes 2
Official- gastrointestinal stromal tumors (C49.A-)Inherited from C15-C26
Related Codes
No related codes are included in this display for C19. Check the Code Book for the complete code path.
Includes
OfficialNo Includes notes are included in this display for C19. Check the code and parent instructions in the Code Book.
Excludes 1
Official- malignant carcinoid tumors of the colon (C7A.02-)
- Kaposi's sarcoma of gastrointestinal sites (C46.4)Inherited from C15-C26
Code First
OfficialNo Code First sequencing instructions are included in this display for C19. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C19. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C19. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is C19 an HCC code?
Yes. C19 (Malignant neoplasm of rectosigmoid junction) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: C19 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C19
- Description
- Malignant neoplasm of rectosigmoid junction
- HCC (V28)
- HCC 22 — Bladder, Colorectal, and Other Cancers
- RAF reference coefficient
- 0.363
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work C19 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C19
For C19, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
C19 is the ICD-10-CM diagnosis code for malignant neoplasm of rectosigmoid junction. Cancer that occurs at the rectosigmoid junction, which is the area where the sigmoid colon meets the rectum. C19 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of digestive organs (c15-c26).
Under the CMS-HCC V28 risk adjustment model, C19 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a source-labeled community, non-dual, aged reference coefficient of 0.363. No V24 mapping is shown for C19; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This code is used when the tumor involves the junction between sigmoid colon and rectum. For C19, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for C19 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code is used when the tumor involves the junction between sigmoid colon and rectum
- •Verify documentation confirms involvement of the junction area rather than just one segment
Clinical Significance
Malignant neoplasm of the rectosigmoid junction is clinically significant because tumors at this boundary zone between the sigmoid colon and rectum may require treatment approaches from both colon and rectal cancer paradigms. The rectosigmoid junction is defined as the area approximately 12-15 cm from the anal verge, and cancers here may be managed with either low anterior resection or sigmoid colectomy depending on exact location and extent. Accurate coding at this specific junction affects treatment decisions and resource allocation.
Documentation Requirements
- ✓Documentation confirming the tumor involves the rectosigmoid junction specifically
- ✓Distance from the anal verge if measured (typically 12-15 cm)
- ✓Histological type and grade
- ✓Stage of disease with circumferential resection margin status
- ✓Whether neoadjuvant chemoradiation was administered (more common for rectal-predominant tumors)
Excludes 1, Do NOT code together
- malignant carcinoid tumors of the colon (C7A.02-)
Commonly Confused Codes
- •C18.7: Sigmoid colon: if the tumor is entirely in the sigmoid without extending to the rectum, use C18.7
- •C20: Rectum: if the tumor is entirely rectal without sigmoid extension, use C20
- •C21.8: Overlapping sites of rectum/anus/anal canal: use when the tumor extends below the rectum to involve anal structures