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C23 ICD-10-CM Code: Malignant neoplasm of gallbladder

C23 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 coding software

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Code lookupC23

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

C23

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

Malignant neoplasm of gallbladder

A cancer that develops in the gallbladder, the small organ that stores bile. It is often diagnosed at an advanced stage because early symptoms are uncommon.

Buddy the Bee presenting code insight

Buddy Insight

Gallbladder cancer is an aggressive malignancy that is often discovered incidentally during cholecystectomy for presumed benign disease.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 20

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

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 009

Code-level coefficient reference

ESRD/PACE

HCC 9

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C2Malignant neoplasms of digestive organs (C15-C26)C23Malignant neoplasm of gallbladder

Inclusion Terms

Official

No inclusion terms are included in this display for C23. 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

No related codes are included in this display for C23. Check the Code Book for the complete code path.

Includes

Official

No Includes notes are included in this display for C23. 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

Code First

Official

No Code First sequencing instructions are included in this display for C23. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C23. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C23. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Pathological confirmation of malignancy (especially in incidental findings during cholecystectomy)
Histological type (adenocarcinoma is most common; also squamous cell, neuroendocrine)
T-stage: depth of gallbladder wall invasion is critical for management decisions
Any history of gallstones, porcelain gallbladder, or primary sclerosing cholangitis

MEAT Support

HCC Buddy guidance
Pathological confirmation of malignancy (especially in incidental findings during cholecystectomy)
Histological type (adenocarcinoma is most common; also squamous cell, neuroendocrine)
T-stage: depth of gallbladder wall invasion is critical for management decisions
Any history of gallstones, porcelain gallbladder, or primary sclerosing cholangitis

Audit Caution

HCC Buddy guidance
Coding an incidental gallbladder polyp found on ultrasound as gallbladder cancer without pathological confirmation
Not recognizing that T1a gallbladder cancer (limited to lamina propria) may be cured by cholecystectomy alone, while T1b and higher require radical resection
Coding bile duct cancer as gallbladder cancer when the primary origin is the bile duct
Using personal history code (Z85.09) when active gallbladder cancer is being treated

Common Mistakes

HCC Buddy guidance
K82.8 — Other specified diseases of gallbladder: benign gallbladder conditions; ensure malignancy is confirmed
C24.0 — Extrahepatic bile duct cancer: gallbladder cancer may involve the cystic duct or common bile duct; code the primary site
C22.1 — Intrahepatic bile duct carcinoma: intrahepatic location, not gallbladder
D13.5 — Benign neoplasm of extrahepatic bile ducts: benign, not malignant; includes gallbladder polyps that are benign

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 C23 an HCC code?

Yes. C23 (Malignant neoplasm of gallbladder) 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: C23 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
C23
Description
Malignant neoplasm of gallbladder
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 C23 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C23

For C23, 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

C23 is the ICD-10-CM diagnosis code for malignant neoplasm of gallbladder. A cancer that develops in the gallbladder, the small organ that stores bile. It is often diagnosed at an advanced stage because early symptoms are uncommon. C23 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, C23 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.

Document any history of gallstones, primary sclerosing cholangitis, or other risk factors. For C23, 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 C23 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Document any history of gallstones, primary sclerosing cholangitis, or other risk factors
  • •Distinguish from bile duct cancers (C24) and liver cancers (C22)

Clinical Significance

Gallbladder cancer is an aggressive malignancy that is often discovered incidentally during cholecystectomy for presumed benign disease. It is the most common biliary tract malignancy and has a poor prognosis when diagnosed at advanced stages because symptoms typically occur late. The anatomical location adjacent to the liver, bile ducts, and major vessels makes surgical management complex, often requiring radical cholecystectomy with liver wedge resection and lymph node dissection.

Documentation Requirements

  • ✓Pathological confirmation of malignancy (especially in incidental findings during cholecystectomy)
  • ✓Histological type (adenocarcinoma is most common; also squamous cell, neuroendocrine)
  • ✓T-stage: depth of gallbladder wall invasion is critical for management decisions
  • ✓Any history of gallstones, porcelain gallbladder, or primary sclerosing cholangitis
  • ✓Whether the diagnosis was incidental at surgery or clinically suspected

Commonly Confused Codes

  • •K82.8: Other specified diseases of gallbladder: benign gallbladder conditions; ensure malignancy is confirmed
  • •C24.0: Extrahepatic bile duct cancer: gallbladder cancer may involve the cystic duct or common bile duct; code the primary site
  • •C22.1: Intrahepatic bile duct carcinoma: intrahepatic location, not gallbladder
  • •D13.5: Benign neoplasm of extrahepatic bile ducts: benign, not malignant; includes gallbladder polyps that are benign

Code Hierarchy

└C23Malignant neoplasm of gallbladder
└C23Malignant neoplasm of gallbladder

For C23, 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.

C23 maps to CMS-HCC V28 category 20, Lung and Other Severe Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C23. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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