2026 ICD-10-CM Diagnosis Code C66.1Malignant neoplasm of right ureter

ICD-10-CM Codes›C00–D49›C64-C68›C66

ICD-10-CM C66.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C66.1 is a billable ICD-10-CM diagnosis code for malignant neoplasm of right ureter. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 656 through 658, 686 through 688. Coders also document this condition as bilateral primary malignant neoplasm of ureters. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Urinary system cancers - ureter and renal pelvis.

Code Identity

ICD-10-CM Code
C66.1
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of right ureter
Short Description
Malignant neoplasm of right ureter
Same as the full description in the CMS dataset.
Parent Code
C66
Malignant neoplasm of ureter

Code Classification

ChapterC00–D49Neoplasms
SectionC64-C68Malignant neoplasms of urinary tract
CategoryC66Malignant neoplasm of ureter
This CodeC66.1Malignant neoplasm of right ureter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bilateral primary malignant neoplasm of ureters
  • Primary malignant neoplasm of left ureter
  • Primary malignant neoplasm of right ureter
  • Primary transitional cell carcinoma of right ureter
  • Primary transitional cell carcinoma of upper urinary tract
  • Primary transitional cell carcinoma of ureter
  • Transitional cell carcinoma of right ureter
  • Transitional cell carcinoma of ureter

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO044
Urinary system cancers - ureter and renal pelvis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

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Convert C66.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
189.2 Malign neopl ureter
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C66.1Overview

Is C66.1 (Malignant neoplasm of ureter) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of right ureter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C66.1 group to?

When malignant neoplasm of right ureter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 656, 657, 658, 686, 687, 688, with relative weights from 0.7903 to 3.1838 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C66.1?

Under the General Equivalence Mappings, malignant neoplasm of right ureter converts to ICD-9-CM 189.2 (malign neopl ureter). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.