C16.4 ICD-10-CM Code: Malignant neoplasm of pylorus
C16.4 maps to CMS-HCC V28 20. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)
C16.4
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of pylorus
Cancer that starts in the pylorus, which is the muscular opening at the bottom of the stomach that controls food passage into the small intestine.
Buddy Insight
Malignant neoplasm of the pylorus affects the muscular sphincter controlling gastric emptying into the duodenum.
CMS-HCC V28
MappedHCC 20
Coefficient HCC 20: 1.136 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 009
Code-level coefficient reference
ESRD/PACE
MappedHCC 9
Code-level coefficient reference
RXHCC
MappedHCC 22
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Malignant neoplasm of prepylorus
- Malignant neoplasm of pyloric canal
Excludes 2
Official- gastrointestinal stromal tumors (C49.A-)Inherited from C15-C26, C16
- malignant carcinoid tumor of the stomach (C7A.092)Inherited from C15-C26, C16
Related Codes
Includes
OfficialNo Includes notes are included in this display for C16.4. Check the code and parent instructions in the Code Book.
Excludes 1
Official- 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 C16.4. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify:Inherited from C16
- alcohol abuse and dependence (F10.-)Inherited from C16
Code Also
OfficialNo Code Also instructions are included in this display for C16.4. 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 C16.4 an HCC code?
Yes. C16.4 (Malignant neoplasm of pylorus) maps to HCC 20, Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.136. 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: C16.4 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C16.4
- Description
- Malignant neoplasm of pylorus
- HCC (V28)
- HCC 20 — Lung and Other Severe Cancers
- RAF reference coefficient
- 1.136
- 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 C16.4 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C16.4
For C16.4, 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
C16.4 is the ICD-10-CM diagnosis code for malignant neoplasm of pylorus. Cancer that starts in the pylorus, which is the muscular opening at the bottom of the stomach that controls food passage into the small intestine. C16.4 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, C16.4 maps to Lung and Other Severe Cancers (HCC 20) with a source-labeled community, non-dual, aged reference coefficient of 1.136. 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.
Verify histological type (adenocarcinoma is most common) and stage when available for complete coding. For C16.4, 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 C16.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify histological type (adenocarcinoma is most common) and stage when available for complete coding
- •Distinguish from other gastric cancer sites; pyloric location may affect treatment approach and prognosis
Clinical Significance
Malignant neoplasm of the pylorus affects the muscular sphincter controlling gastric emptying into the duodenum. Pyloric cancers frequently cause obstruction and can mimic benign pyloric stenosis, making biopsy confirmation essential. This specific location has implications for surgical planning, as pyloric tumors may require distal gastrectomy with reconstruction of the gastric outlet.
Documentation Requirements
- ✓Documentation confirming the pylorus specifically (not pyloric antrum)
- ✓Histological confirmation of malignancy
- ✓Presence or absence of obstruction
- ✓Stage of disease
- ✓Treatment status and surgical approach if applicable
Commonly Confused Codes
- •C16.3: Pyloric antrum: the antrum is the wider proximal region; the pylorus is the narrow sphincter itself
- •C17.0: Duodenum: tumors may extend from pylorus into duodenum; code the primary site of origin
- •K31.1: Adult hypertrophic pyloric stenosis: benign condition, not malignant; confirm pathology for malignancy