Skip to content
HCC Buddy home

C66.1 ICD-10-CM Code: Malignant neoplasm of right ureter

C66.1 maps to CMS-HCC V28 22. 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 lookupC66.1

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of urinary tract (C64-C68)

C66.1

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

Malignant neoplasm of right ureter

This code represents cancer that has developed in the right ureter, which is the tube that carries urine from the right kidney to the bladder. It is a malignant (cancerous) tumor that requires treatment.

Buddy the Bee presenting code insight

Buddy Insight

Right ureteral cancer is an upper tract urothelial carcinoma arising from the tube connecting the kidney to the bladder.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 22

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 012

Code-level coefficient reference

ESRD/PACE

HCC 11

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C66Malignant neoplasm of ureterC66.1Malignant neoplasm of right ureter

Inclusion Terms

Official

No inclusion terms are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Related Codes

Official
C66.2Malignant neoplasm of left ureterC66.9Malignant neoplasm of unspecified ureter

Includes

Official

No Includes notes are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • malignant neoplasm of ureteric orifice of bladder (C67.6)Inherited from C66

Code First

Official

No Code First sequencing instructions are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C66.1. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Pathology confirming right ureteral malignancy
Histologic type (urothelial carcinoma expected in most cases)
Location within the ureter (proximal, mid, or distal third)
Staging and grade

MEAT Support

HCC Buddy guidance
Pathology confirming right ureteral malignancy
Histologic type (urothelial carcinoma expected in most cases)
Location within the ureter (proximal, mid, or distal third)
Staging and grade

Audit Caution

HCC Buddy guidance
Confusing ureteral cancer with renal pelvis cancer — they are distinct anatomical locations within the upper urinary tract
Using unspecified laterality when the side is documented
Coding ureteral obstruction caused by the cancer as the primary diagnosis instead of the malignancy
Not recognizing that distal ureteral tumors may be confused with bladder trigone tumors

Common Mistakes

HCC Buddy guidance
C65.1 — Right renal pelvis cancer; ureter and renal pelvis are contiguous but coded separately
C66.2 — Left ureter cancer; verify laterality
C66.9 — Unspecified ureter; use C66.1 when right is documented
C67.5 — Bladder neck cancer; distal ureteral tumors near the ureteral orifice may be confused with bladder tumors

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 C66.1 an HCC code?

Yes. C66.1 (Malignant neoplasm of right ureter) maps to HCC 22, Bladder, Colorectal, and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.363. 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: C66.1 is billable and maps to V28 HCC 22, Bladder, Colorectal, and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C66.1
Description
Malignant neoplasm of right ureter
HCC (V28)
HCC 22 — Bladder, Colorectal, and Other Cancers
RAF reference coefficient
0.363
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 22, Bladder, Colorectal, and Other Cancers
0.363
ESRDHCC 11, Colorectal/Bladder/and Other 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 C66.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C66.1

For C66.1, 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

C66.1 is the ICD-10-CM diagnosis code for malignant neoplasm of right ureter. This code represents cancer that has developed in the right ureter, which is the tube that carries urine from the right kidney to the bladder. It is a malignant (cancerous) tumor that requires treatment. C66.1 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of urinary tract (c64-c68).

Under the CMS-HCC V28 risk adjustment model, C66.1 maps to Bladder, Colorectal, and Other Cancers (HCC 22) with a source-labeled community, non-dual, aged reference coefficient of 0.363. No V24 mapping is shown for C66.1; use the applicable model and payment year when reviewing the V28 mapping. 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.

Ensure laterality is documented in the medical record as 'right' to support the use of this specific code; do not use this code for left ureter (C66.2) or unspecified side (C66.9). For C66.1, 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 C66.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Ensure laterality is documented in the medical record as 'right' to support the use of this specific code; do not use this code for left ureter (C66.2) or unspecified side (C66.9)
  • •This code should be used as the primary diagnosis for cancer cases; pair with additional codes for histology type, stage, and any metastases as documented by the physician

Clinical Significance

Right ureteral cancer is an upper tract urothelial carcinoma arising from the tube connecting the kidney to the bladder. Like renal pelvis urothelial cancer, it carries significant risk for metachronous bladder cancer. Ureteral tumors are less common than renal pelvis or bladder cancers but share the same urothelial biology and require similar surveillance protocols.

Documentation Requirements

  • ✓Pathology confirming right ureteral malignancy
  • ✓Histologic type (urothelial carcinoma expected in most cases)
  • ✓Location within the ureter (proximal, mid, or distal third)
  • ✓Staging and grade
  • ✓Hydronephrosis status
  • ✓Treatment plan (nephroureterectomy with bladder cuff excision is standard)

Commonly Confused Codes

  • •C65.1: Right renal pelvis cancer; ureter and renal pelvis are contiguous but coded separately
  • •C66.2: Left ureter cancer; verify laterality
  • •C66.9: Unspecified ureter; use C66.1 when right is documented
  • •C67.5: Bladder neck cancer; distal ureteral tumors near the ureteral orifice may be confused with bladder tumors
  • •N13.1: Hydronephrosis with ureteral stricture; ureteral obstruction from cancer, not a separate code for the obstruction

Child Codes

C66.1Malignant neoplasm of right ureter
HCC 22
C66.2Malignant neoplasm of left ureter
HCC 22
C66.9Malignant neoplasm of unspecified ureter
HCC 22

Code Hierarchy

└C66Malignant neoplasm of ureter└C66.1Malignant neoplasm of right ureter
└C66.1Malignant neoplasm of right ureter

For C66.1, 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.

C66.1 maps to CMS-HCC V28 category 22, Bladder, Colorectal, and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C66.1. 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.

Work C66.1 in HCC Buddy

Open C66.1 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro