C24.1
BillableMalignant neoplasm of ampulla of Vater
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C24.1 an HCC code?
Yes. C24.1 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 C24.1
For C24.1 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 C24.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C24.1 is the ICD-10-CM diagnosis code for malignant neoplasm of ampulla of vater. Cancer that develops in the ampulla of Vater, which is the small opening where the pancreatic and bile ducts enter the small intestine. C24.1 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, C24.1 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, C24.1 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.
The ampulla of Vater is a specific anatomical location at the junction of multiple ducts. Because C24.1 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 C24.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The ampulla of Vater is a specific anatomical location at the junction of multiple ducts
- •This location may present with jaundice and digestive symptoms due to obstruction of bile and pancreatic flow
Clinical Significance
Malignant neoplasm of the ampulla of Vater is a periampullary cancer at the junction where the common bile duct and pancreatic duct enter the duodenum. Ampullary cancers are clinically significant because they often present relatively early with jaundice due to bile duct obstruction, giving them a better prognosis than pancreatic cancer. Treatment typically involves pancreaticoduodenectomy (Whipple procedure), which is one of the most complex abdominal surgeries, justifying the high risk adjustment weight.
Documentation Requirements
- ✓Documentation confirming the ampulla of Vater as the primary tumor origin
- ✓Histological type (intestinal type vs pancreatobiliary type — affects prognosis)
- ✓Distinction from duodenal, pancreatic head, or common bile duct cancer
- ✓Stage of disease
- ✓Resectability and surgical approach
Commonly Confused Codes
- •C25.0 — Head of pancreas: periampullary tumors may arise from the pancreas, ampulla, duodenum, or bile duct — the primary site determines the code
- •C17.0 — Duodenum: periampullary duodenal cancer is coded to the duodenum, not the ampulla
- •C24.0 — Extrahepatic bile duct: distal bile duct cancer near the ampulla may be confused with ampullary cancer
- •D13.5 — Benign neoplasm of extrahepatic bile ducts: includes benign ampullary adenomas, which are not malignant