What is ICD-10 code C49.A2?

C49.A2 is the ICD-10-CM diagnosis code for Gastrointestinal stromal tumor of stomach. It belongs to the ICD-10-CM chapter for neoplasms (c00-d49). C49.A2 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. C49.A2 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. C49.A2 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. C49.A2 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.

What is the V28 vs V24 difference for C49.A2?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For C49.A2, V28 maps to Prostate, Breast, and Other Cancers and Tumors at RAF 0.186 while V24 mapped to Lymphoma and Other Cancers at RAF 0.675. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting C49.A2?

Verify the tumor location is specifically the stomach; GISTs can occur in other parts of the digestive tract and require different codes (C49.A1 for esophagus, C49.A3 for small intestine, etc.) Ensure documentation includes whether the tumor is benign, uncertain behavior, or malignant, as this affects code selection and staging requirements Because C49.A2 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM C49.A2: Gastrointestinal stromal

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC49.A2Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of mesothelial and soft tissue (C45-C49)

C49.A2

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

Gastrointestinal stromal tumor of stomach

A gastrointestinal stromal tumor (GIST) is a rare type of cancer that develops in the stomach from specialized nerve cells. These tumors can vary in size and aggressiveness, and may require surgery or targeted medication to treat.

Buddy Insight

Gastrointestinal stromal tumor of the stomach is the most common GIST location, accounting for approximately 60-70% of all GISTs.

CMS-HCC V28

Mapped

HCC 23

Prostate, Breast, and Other C...

RAF 0.186

CMS-HCC V24

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.675

ACA/HHS

Mapped

HCC 10

HHS-HCC 10

Varies by metal level

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

RAF 0.111

RXHCC

Mapped

HCC 20

Cancer, Liver and Intrahepati...

RAF 0.491

Code Book Path

Official

C49Malignant neoplasm of other connective and soft tissue

C49.AGastrointestinal stromal tumor

C49.A2Gastrointestinal stromal tumor of stomach

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for C49.A2 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for C49.A2 in this effective period.

Related Child Codes

Official

C49.A0Gastrointestinal stromal tumor, unspecified site

C49.A1Gastrointestinal stromal tumor of esophagus

C49.A3Gastrointestinal stromal tumor of small intestine

C49.A4Gastrointestinal stromal tumor of large intestine

C49.A5Gastrointestinal stromal tumor of rectum

Includes

Official

ICD-10-CM does not list Includes notes for C49.A2 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for C49.A2 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for C49.A2 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for C49.A2 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for C49.A2 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Pathology confirming GIST of gastric origin with immunohistochemistry (KIT/CD117, DOG1)

Specific gastric location (fundus, body, antrum, cardia)

Tumor size (critical for risk: <2cm, 2-5cm, 5-10cm, >10cm)

Mitotic rate per 50 high-power fields

MEAT Support

HCC Buddy guidance

Pathology confirming GIST of gastric origin with immunohistochemistry (KIT/CD117, DOG1)

Specific gastric location (fundus, body, antrum, cardia)

Tumor size (critical for risk: <2cm, 2-5cm, 5-10cm, >10cm)

Mitotic rate per 50 high-power fields

Audit Caution

HCC Buddy guidance

Confusing gastric GIST with gastric adenocarcinoma — GIST is a mesenchymal tumor, adenocarcinoma is epithelial

Using the generic stomach cancer code (C16) instead of the GIST-specific code (C49.A2)

Coding a small incidentally discovered GIST (<2cm) as malignant without pathology supporting malignant behavior

Not distinguishing between malignant GIST and uncertain behavior GIST (which would use D48 codes)

Common Mistakes

HCC Buddy guidance

C16._ (Malignant neoplasm of stomach) — gastric adenocarcinoma, not GIST

C49.A0 (GIST, unspecified site) — use C49.A2 when stomach is documented

C49.A3 (GIST of small intestine) — different site with different prognosis

D21.4 (Benign neoplasm of connective tissue of abdomen) — benign tumor, not malignant GIST

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 C49.A2 an HCC code?

Yes. C49.A2 (Gastrointestinal stromal tumor of stomach) maps to Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Lymphoma and Other Cancers under V24), with a community non-dual aged RAF of 0.186. It is billable for payment year 2026.

Coder answer: C49.A2 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C49.A2
Description: Gastrointestinal stromal tumor of stomach
HCC (V28): HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF: 0.186
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors

0.186

V24HCC 10, Lymphoma and Other Cancers

0.675

ESRDHCC 10, Lymphoma and Other Cancers

0.111

RxHCCHCC 20, Cancer, Liver and Intrahepatic Bile Duct

0.491

Each model's RAF is its CMS base weight for that model's standard population, so 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 segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work C49.A2 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for C49.A2

For C49.A2 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

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

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C49.A2 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

Get the V28 RAF + MEAT cheat sheet

One printable page: confirm a code's V28 HCC status, its RAF weight, and the MEAT your note needs to make it stick. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

C49.A2 is the ICD-10-CM diagnosis code for gastrointestinal stromal tumor of stomach. A gastrointestinal stromal tumor (GIST) is a rare type of cancer that develops in the stomach from specialized nerve cells. These tumors can vary in size and aggressiveness, and may require surgery or targeted medication to treat. C49.A2 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of mesothelial and soft tissue (c45-c49).

Under the CMS-HCC V28 risk adjustment model, C49.A2 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a community, non-dual, aged base RAF weight of 0.186. Under the older CMS-HCC V24 model, C49.A2 maps to Lymphoma and Other Cancers (HCC 10) with a community, non-dual, aged base RAF weight of 0.675. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Verify the tumor location is specifically the stomach; GISTs can occur in other parts of the digestive tract and require different codes (C49.A1 for esophagus, C49.A3 for small intestine, etc.). Because C49.A2 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for C49.A2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify the tumor location is specifically the stomach; GISTs can occur in other parts of the digestive tract and require different codes (C49.A1 for esophagus, C49.A3 for small intestine, etc.)
•Ensure documentation includes whether the tumor is benign, uncertain behavior, or malignant, as this affects code selection and staging requirements

Clinical Significance

Gastrointestinal stromal tumor of the stomach is the most common GIST location, accounting for approximately 60-70% of all GISTs. Gastric GISTs generally have a better prognosis than small intestinal GISTs of the same size and mitotic rate, making accurate site-specific coding important for prognostic stratification.

Documentation Requirements

✓Pathology confirming GIST of gastric origin with immunohistochemistry (KIT/CD117, DOG1)
✓Specific gastric location (fundus, body, antrum, cardia)
✓Tumor size (critical for risk: <2cm, 2-5cm, 5-10cm, >10cm)
✓Mitotic rate per 50 high-power fields
✓Treatment plan (surgical resection, imatinib therapy, observation for small tumors)

Commonly Confused Codes

•C16._ (Malignant neoplasm of stomach): gastric adenocarcinoma, not GIST
•C49.A0 (GIST, unspecified site): use C49.A2 when stomach is documented
•C49.A3 (GIST of small intestine): different site with different prognosis
•D21.4 (Benign neoplasm of connective tissue of abdomen): benign tumor, not malignant GIST