C16.8
BillableMalignant neoplasm of overlapping sites of stomach
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C16.8 an HCC code?
Yes. C16.8 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lung and Other Severe Cancers under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for C16.8
For C16.8 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 C16.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C16.8 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of stomach. Cancer that involves multiple overlapping sites within the stomach rather than being confined to a single location. C16.8 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, C16.8 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, C16.8 mapped to the same category but with a base RAF weight of 0.973 — V28 recalibrated weights across the entire model. 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.
This code indicates involvement of two or more distinct stomach regions; document which sites are involved. Because C16.8 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 C16.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code indicates involvement of two or more distinct stomach regions; document which sites are involved
- •Overlapping tumors typically indicate more advanced disease and should be staged accordingly
Clinical Significance
Overlapping sites of stomach indicates a gastric cancer that spans multiple anatomical regions, typically reflecting more advanced disease with larger tumor burden. These tumors are often more difficult to manage surgically and may require total gastrectomy rather than subtotal resection. Capturing this code accurately reflects the increased complexity and resource utilization associated with multi-region gastric involvement.
Documentation Requirements
- ✓Documentation confirming involvement of two or more distinct gastric regions
- ✓Specification of which regions are involved
- ✓Histological type (particularly distinguishing diffuse from intestinal type)
- ✓Stage of disease with tumor dimensions
- ✓Surgical approach and treatment plan
Commonly Confused Codes
- •C16.9 — Stomach, unspecified: C16.8 is for known multi-region involvement; C16.9 is for unknown location — do not confuse these
- •C16.0-C16.6 — Specific gastric sites: use site-specific codes when the tumor is confined to one region
- •C15.8 — Overlapping sites of esophagus: use when the tumor is in the esophagus, not the stomach