What is ICD-10 code C16.5?

C16.5 is the ICD-10-CM diagnosis code for Malignant neoplasm of lesser curvature of stomach, unspecified. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C16.5 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C16.5 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. C16.5 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. C16.5 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does C16.5 map to under V28?

C16.5 maps to CMS-HCC V28 HCC 20 (Lung and Other Severe Cancers). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM C16.5: Malignant neoplasm of lesser

C16.5 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 · free HCC coding tools

ICD-10-CM Code View

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Code lookupC16.5

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)

C16.5

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of lesser curvature of stomach, unspecified

This code represents cancer that has developed on the lesser curvature, which is the inner curved edge of the stomach. It is used when the specific type of stomach cancer cells has not been further specified.

Buddy Insight

Cancer of the lesser curvature of the stomach is notable because this medial surface is a common site for gastric ulcers and subsequent malignant transformation.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 009

HHS-HCC 009 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 9

Lung and Other Severe Cancers

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C16Malignant neoplasm of stomach C16.5Malignant neoplasm of lesser curvature of stomach, unspecified

Inclusion Terms

Official

Malignant neoplasm of lesser curvature of stomach, not classifiable to C16.1-C16.4

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

Official

C16.0Malignant neoplasm of cardia C16.1Malignant neoplasm of fundus of stomach C16.2Malignant neoplasm of body of stomach C16.3Malignant neoplasm of pyloric antrum C16.4Malignant neoplasm of pylorus

Includes

Official

No Includes notes are included in this display for C16.5. 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

Official

No Code First sequencing instructions are included in this display for C16.5. 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

Official

No Code Also instructions are included in this display for C16.5. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation specifying lesser curvature location

Whether the lesion is further specified by longitudinal segment (cardia, body, antrum)

Histological type confirmed by biopsy

Stage of disease

MEAT Support

HCC Buddy guidance

Documentation specifying lesser curvature location

Whether the lesion is further specified by longitudinal segment (cardia, body, antrum)

Histological type confirmed by biopsy

Stage of disease

Audit Caution

HCC Buddy guidance

Confusing lesser and greater curvature — lesser is the shorter, concave inner border; greater is the longer, convex outer border

Defaulting to C16.9 when the curvature is documented but the longitudinal segment is not — the curvature code is more specific than unspecified

Not recognizing that endoscopy reports may describe location by curvature rather than by anatomical segment

Common Mistakes

HCC Buddy guidance

C16.6 — Greater curvature: the greater curvature is the outer (lateral) curve; the lesser curvature is the inner (medial) curve

C16.2 — Body of stomach: if documentation specifies both body and lesser curvature, the more specific longitudinal segment may be preferred

C16.9 — Stomach, unspecified: use C16.5 when lesser curvature is documented even if longitudinal segment is not

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 C16.5 an HCC code?

Yes. C16.5 (Malignant neoplasm of lesser curvature 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: C16.5 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: C16.5
Description: Malignant neoplasm of lesser curvature 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

V28HCC 20, Lung and Other Severe Cancers

1.136

ESRDHCC 9, Lung and Other Severe Cancers

Not separately weighted

RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors

Not separately weighted

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 C16.5 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C16.5

For C16.5, 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

C16.5 is the ICD-10-CM diagnosis code for malignant neoplasm of lesser curvature of stomach, unspecified. This code represents cancer that has developed on the lesser curvature, which is the inner curved edge of the stomach. It is used when the specific type of stomach cancer cells has not been further specified. C16.5 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, C16.5 maps to Lung and Other Severe Cancers (HCC 20) with a source-labeled community, non-dual, aged reference coefficient of 1.136. No V24 mapping is shown for C16.5; 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.

Verify documentation specifies the lesser curvature location; if the exact location is not documented, use C16.9 (stomach, unspecified site) instead. For C16.5, 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 C16.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify documentation specifies the lesser curvature location; if the exact location is not documented, use C16.9 (stomach, unspecified site) instead
•If histological type is documented (e.g., adenocarcinoma, squamous cell), use the appropriate C16.5 subcode with the 5th character for histology rather than 'unspecified'

Clinical Significance

Cancer of the lesser curvature of the stomach is notable because this medial surface is a common site for gastric ulcers and subsequent malignant transformation. The lesser curvature is anatomically significant due to its rich lymphatic drainage, which can facilitate early metastatic spread. Coding by curvature rather than longitudinal segment reflects a different anatomical classification system used in some clinical documentation.

Documentation Requirements

✓Documentation specifying lesser curvature location
✓Whether the lesion is further specified by longitudinal segment (cardia, body, antrum)
✓Histological type confirmed by biopsy
✓Stage of disease
✓Any history of gastric ulcer disease at this location

Commonly Confused Codes

•C16.6: Greater curvature: the greater curvature is the outer (lateral) curve; the lesser curvature is the inner (medial) curve
•C16.2: Body of stomach: if documentation specifies both body and lesser curvature, the more specific longitudinal segment may be preferred
•C16.9: Stomach, unspecified: use C16.5 when lesser curvature is documented even if longitudinal segment is not