C49.A0 ICD-10-CM Code: Gastrointestinal stromal tumor, unspecified site
C49.A0 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of mesothelial and soft tissue (C45-C49)
C49.A0
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceGastrointestinal stromal tumor, unspecified site
A gastrointestinal stromal tumor (GIST), a specific type of soft tissue cancer that arises in the digestive tract, when the exact location within the GI system is not specified.
Buddy Insight
Gastrointestinal stromal tumor (GIST), unspecified site is a distinct mesenchymal neoplasm arising from the interstitial cells of Cajal.
CMS-HCC V28
MappedHCC 23
Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 010
Code-level coefficient reference
ESRD/PACE
MappedHCC 10
Code-level coefficient reference
RXHCC
MappedHCC 20
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C49.A0. Check the code and parent instructions in the Code Book.
Excludes 2
Official- Kaposi's sarcoma of soft tissue (C46.1)Inherited from C49
- malignant neoplasm of heart (C38.0)Inherited from C49
- malignant neoplasm of peripheral nerves and autonomic nervous system (C47.-)Inherited from C49
- malignant neoplasm of peritoneum (C48.2)Inherited from C49
- malignant neoplasm of retroperitoneum (C48.0)Inherited from C49
- malignant neoplasm of uterine ligament (C57.3)Inherited from C49
- mesothelioma (C45.-)Inherited from C49
Related Codes
Includes
Official- malignant neoplasm of blood vesselInherited from C49
- malignant neoplasm of bursaInherited from C49
- malignant neoplasm of cartilageInherited from C49
- malignant neoplasm of fasciaInherited from C49
- malignant neoplasm of fatInherited from C49
- malignant neoplasm of ligament, except uterineInherited from C49
- malignant neoplasm of lymphatic vesselInherited from C49
- malignant neoplasm of muscleInherited from C49
- malignant neoplasm of synoviaInherited from C49
- malignant neoplasm of tendon (sheath)Inherited from C49
Excludes 1
Official- malignant neoplasm of cartilage (of):Inherited from C49
- articular (C40-C41)Inherited from C49
- larynx (C32.3)Inherited from C49
- nose (C30.0)Inherited from C49
- malignant neoplasm of connective tissue of breast (C50.-)Inherited from C49
Code First
OfficialNo Code First sequencing instructions are included in this display for C49.A0. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for C49.A0. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for C49.A0. 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 C49.A0 an HCC code?
Yes. C49.A0 (Gastrointestinal stromal tumor, unspecified site) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. 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: C49.A0 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.A0
- Description
- Gastrointestinal stromal tumor, unspecified site
- HCC (V28)
- HCC 23 — Prostate, Breast, and Other Cancers and Tumors
- RAF reference coefficient
- 0.186
- 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 C49.A0 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C49.A0
For C49.A0, 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
C49.A0 is the ICD-10-CM diagnosis code for gastrointestinal stromal tumor, unspecified site. A gastrointestinal stromal tumor (GIST), a specific type of soft tissue cancer that arises in the digestive tract, when the exact location within the GI system is not specified. C49.A0 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.A0 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. 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.
GISTs are a distinct subtype of soft tissue sarcoma; ensure pathology confirms GIST diagnosis. For C49.A0, 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 C49.A0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •GISTs are a distinct subtype of soft tissue sarcoma; ensure pathology confirms GIST diagnosis
- •If the specific GI site is documented, use the more specific C49.A1-A9 codes instead of A0
Clinical Significance
Gastrointestinal stromal tumor (GIST), unspecified site is a distinct mesenchymal neoplasm arising from the interstitial cells of Cajal. GIST is the most common mesenchymal tumor of the gastrointestinal tract and has specific molecular markers (KIT/CD117, DOG1) and targeted therapy (imatinib), making accurate identification critical for treatment planning.
Documentation Requirements
- ✓Pathology confirming GIST with immunohistochemistry (KIT/CD117 positive, DOG1)
- ✓Anatomical site of the GIST — query if not documented (stomach is most common)
- ✓Tumor size (critical for risk stratification: <2cm, 2-5cm, 5-10cm, >10cm)
- ✓Mitotic rate (per 50 high-power fields — key prognostic factor)
- ✓Mutation testing results (KIT exon 11, exon 9, PDGFRA) if performed
Commonly Confused Codes
- •C49.A1-C49.A5 (Site-specific GIST codes): always preferred when the gastrointestinal site is documented
- •C49.4 (Malignant neoplasm of connective/soft tissue of abdomen): general soft tissue sarcoma, not GIST
- •C15-C20 (Malignant neoplasms of digestive organs): adenocarcinomas and epithelial cancers, not GIST
- •D21.4 (Benign neoplasm of connective/soft tissue of abdomen): benign tumor, not GIST