C16.9 ICD-10-CM Code: Malignant neoplasm of stomach, unspecified
C16.9 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 Buddy coding tools
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)
C16.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of stomach, unspecified
Stomach cancer when the specific location within the stomach cannot be determined or is not documented.
Buddy Insight
Unspecified stomach cancer indicates documentation does not identify the specific anatomical region within the stomach.
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- Gastric cancer NOS
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 C16.9. 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 C16.9. 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 C16.9. 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 C16.9 an HCC code?
Yes. C16.9 (Malignant neoplasm of stomach, unspecified) 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: C16.9 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
- C16.9
- Description
- Malignant neoplasm of stomach, unspecified
- 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 C16.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C16.9
For C16.9, 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
Get the V28 mapping + MEAT cheat sheet
One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.
Free PDF. No card. Unsubscribe anytime.
What This Code Means
C16.9 is the ICD-10-CM diagnosis code for malignant neoplasm of stomach, unspecified. Stomach cancer when the specific location within the stomach cannot be determined or is not documented. C16.9 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, C16.9 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.
This is a default code; attempt to obtain more specific anatomical location from pathology or imaging reports. For C16.9, 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 C16.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a default code; attempt to obtain more specific anatomical location from pathology or imaging reports
- •Use only when no other C16 code can be assigned due to lack of site specification
Clinical Significance
Unspecified stomach cancer indicates documentation does not identify the specific anatomical region within the stomach. While this code captures the same HCC as specified gastric cancer codes, it represents a documentation quality gap. Gastric cancer overall has significant mortality and morbidity, requiring complex multimodal treatment with surgery, chemotherapy, and sometimes radiation, all of which justify the high risk adjustment weight.
Documentation Requirements
- ✓Confirmed diagnosis of gastric malignancy
- ✓Review of endoscopy, imaging, pathology, and operative reports for specific site information before defaulting to unspecified
- ✓Histological type if available
- ✓Stage of disease
- ✓Current treatment status
Commonly Confused Codes
- •C16.0-C16.6: Specific gastric sites: always use the more specific code when any anatomical detail is available
- •C16.8: Overlapping sites: use when multiple regions are involved, not when region is unknown
- •C78.6: Secondary malignant neoplasm of retroperitoneum and peritoneum: metastatic disease to stomach area should not be coded as primary gastric cancer
- •Z85.028: Personal history of other malignant neoplasm of stomach: use when cancer is resolved