C24.1 maps to CMS-HCC V28 20. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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 lookupC24.1

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of digestive organs (C15-C26)

C24.1

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

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.

Buddy Insight

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.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

Coefficient HCC 20: 1.136 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 009

HHS-HCC 009 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 9

Lung and Other Severe Cancers

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C24Malignant neoplasm of other and unspecified parts of biliary tract C24.1Malignant neoplasm of ampulla of Vater

Inclusion Terms

Official

No inclusion terms are included in this display for C24.1. Check the code and parent instructions in the Code Book.

Excludes 2

Official

gastrointestinal stromal tumors (C49.A-)Inherited from C15-C26

Related Codes

Official

C24.0Malignant neoplasm of extrahepatic bile duct C24.8Malignant neoplasm of overlapping sites of biliary tract C24.9Malignant neoplasm of biliary tract, unspecified

Includes

Official

No Includes notes are included in this display for C24.1. Check the code and parent instructions in the Code Book.

Excludes 1

Official

Kaposi's sarcoma of gastrointestinal sites (C46.4)Inherited from C15-C26, C24
malignant neoplasm of intrahepatic bile duct (C22.1)Inherited from C15-C26, C24

Code First

Official

No Code First sequencing instructions are included in this display for C24.1. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C24.1. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C24.1. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

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

MEAT Support

HCC Buddy guidance

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

Audit Caution

HCC Buddy guidance

Coding pancreatic head cancer as ampullary cancer — these are distinct primary sites with different prognoses

Confusing periampullary cancer (a broader term including multiple possible sites) with true ampullary cancer

Not recognizing that ampullary cancers generally have a better prognosis than pancreatic cancer despite similar treatment

Using the unspecified biliary tract code (C24.9) when the ampulla is specifically documented

Common Mistakes

HCC Buddy guidance

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

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 C24.1 an HCC code?

Yes. C24.1 (Malignant neoplasm of ampulla of Vater) maps to HCC 20, Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.136. 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: C24.1 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C24.1
Description: Malignant neoplasm of ampulla of Vater
HCC (V28): HCC 20 — Lung and Other Severe Cancers
RAF reference coefficient: 1.136
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 20, Lung and Other Severe Cancers

1.136

ESRDHCC 9, Lung and Other Severe Cancers

Not separately weighted

RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors

Not separately weighted

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 C24.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C24.1

For C24.1, 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

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

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 source-labeled community, non-dual, aged reference coefficient of 1.136. 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.

The ampulla of Vater is a specific anatomical location at the junction of multiple ducts. For C24.1, 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 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