2026 ICD-10-CM Diagnosis Code N64.9Disorder of breast, unspecified

ICD-10-CM Codes›N00–N99›N60-N65›N64

ICD-10-CM N64.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N64.9 is a billable ICD-10-CM diagnosis code for disorder of breast, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 600 through 601. Coders also document this condition as abnormal nipple. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nonmalignant breast conditions.

This medical diagnosis code is frequently used in OB/GYN medical specialties to designate conditions such lump in breast and other disorders of the breast.

Code Identity

ICD-10-CM Code
N64.9
Billable Status
Yes — Valid for Submission
Code Describes
Disorder of breast, unspecified
Short Description
Disorder of breast, unspecified
Same as the full description in the CMS dataset.
Parent Code
N64
Other disorders of breast

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN60-N65Disorders of breast
CategoryN64Other disorders of breast
This CodeN64.9Disorder of breast, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormal nipple
  • Breast problem
  • Chronic disease of breast
  • Disorder of breast
  • Disorder of nipple
  • Lesion of breast
  • Nipple problem
  • Problem of chest

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Disease, diseased
      • breast
    • Disease, diseased
      • nipple
    • Disorder(of)
      • breast
    • Mastopathy, mastopathia

Clinical ClassificationClinical

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

CCSR GEN017
Nonmalignant breast conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Breast Diseases

Breast diseases include various conditions and changes in your breast. Most women experience breast changes at some time. Your age, hormone levels, and medicines you take may cause lumps, bumps, and discharges of fluids that are not breast milk.

The full article covers:

  • What are breast diseases?
  • What are the symptoms of breast disease?
  • How are breast diseases diagnosed?
  • What are the treatments for breast disease?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert N64.9 to ICD-9-CMHistory

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

ICD-9-CM
611.9 Breast disorder NOS
Exact Match The mapping is direct, with no qualifiers.

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 N64.9Overview

Is N64.9 (Other disorders of breast) a billable code?

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

What MS-DRG does N64.9 group to?

When disorder of breast, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 600, 601, with relative weights from 0.6050 to 1.0416 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of N64.9?

Under the General Equivalence Mappings, disorder of breast, unspecified converts to ICD-9-CM 611.9 (breast disorder NOS). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.