C16.4
BillableMalignant neoplasm of pylorus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C16.4 an HCC code?
Yes. C16.4 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 C16.4
For C16.4 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 C16.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C16.4 is the ICD-10-CM diagnosis code for malignant neoplasm of pylorus. Cancer that starts in the pylorus, which is the muscular opening at the bottom of the stomach that controls food passage into the small intestine. C16.4 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, C16.4 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, C16.4 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.
Verify histological type (adenocarcinoma is most common) and stage when available for complete coding. Because C16.4 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 C16.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify histological type (adenocarcinoma is most common) and stage when available for complete coding
- •Distinguish from other gastric cancer sites; pyloric location may affect treatment approach and prognosis
Clinical Significance
Malignant neoplasm of the pylorus affects the muscular sphincter controlling gastric emptying into the duodenum. Pyloric cancers frequently cause obstruction and can mimic benign pyloric stenosis, making biopsy confirmation essential. This specific location has implications for surgical planning, as pyloric tumors may require distal gastrectomy with reconstruction of the gastric outlet.
Documentation Requirements
- ✓Documentation confirming the pylorus specifically (not pyloric antrum)
- ✓Histological confirmation of malignancy
- ✓Presence or absence of obstruction
- ✓Stage of disease
- ✓Treatment status and surgical approach if applicable
Commonly Confused Codes
- •C16.3 — Pyloric antrum: the antrum is the wider proximal region; the pylorus is the narrow sphincter itself
- •C17.0 — Duodenum: tumors may extend from pylorus into duodenum; code the primary site of origin
- •K31.1 — Adult hypertrophic pyloric stenosis: benign condition, not malignant; confirm pathology for malignancy