2026 ICD-10-CM Diagnosis Code N61.0Mastitis without abscess

ICD-10-CM Codes›N00–N99›N60-N65›N61

ICD-10-CM N61.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N61.0 is a billable ICD-10-CM diagnosis code for mastitis without abscess. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nonmalignant breast conditions.

Code Identity

ICD-10-CM Code
N61.0
Billable Status
Yes — Valid for Submission
Code Describes
Mastitis without abscess
Short Description
Mastitis without abscess
Same as the full description in the CMS dataset.
Parent Code
N61
Inflammatory disorders of breast

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN60-N65Disorders of breast
CategoryN61Inflammatory disorders of breast
This CodeN61.0Mastitis without abscess

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Actinobacillary mastitis
  • Actinobacillus infection
  • Acute adolescent mastitis
  • Acute mastitis
  • Acute non-puerperal breast abscess
  • Acute non-puerperal mastitis
  • Adolescent mastitis
  • Breast infection
  • Cellulitis of breast
  • Cellulitis of pectoral region
  • Coliform mastitis
  • Corynebacterial mastitis
  • Galactophoritis
  • Infected gland of Montgomery
  • Infective mastitis
  • Inflammation of gland of Montgomery
  • Inflammatory disorder of breast
  • Mastitis of mumps
  • Mycoplasma mastitis
  • Nipple infection
  • Nonpuerperal abscess of areola
  • Nonpuerperal abscess of breast
  • Nonpuerperal mastitis
  • Nonpuerperal mastitis of left breast
  • Nonpuerperal mastitis of right breast
  • Obstetric infection of breast
  • Obstetric mastitis
  • Pseudomonas aeruginosa mastitis
  • Retromammary mastitis
  • Staphylococcal mastitis
  • Subacute mastitis
  • Subacute non-puerperal mastitis
  • Subareolar mastitis
  • Thelitis
  • Ulcer of nipple
  • Ulceration of breast

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Infective mastitis (acute) (nonpuerperal) (subacute)
  • Mastitis (acute) (nonpuerperal) (subacute) NOS
  • Cellulitis (acute) (nonpuerperal) (subacute) of breast NOS
  • Cellulitis (acute) (nonpuerperal) (subacute) of nipple NOS

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.

    • Cellulitis(diffuse) (phlegmonous) (septic) (suppurative)
      • breast (acute) (nonpuerperal) (subacute)
    • Cellulitis(diffuse) (phlegmonous) (septic) (suppurative)
      • breast (acute) (nonpuerperal) (subacute)
        • nipple
    • Cellulitis(diffuse) (phlegmonous) (septic) (suppurative)
      • nipple (acute) (nonpuerperal) (subacute)
    • Fistula(cutaneous)
      • breast
    • Fistula(cutaneous)
      • mammary (gland)
    • Galactophoritis
    • Infection, infected, infective(opportunistic)
      • mammary gland
    • Infection, infected, infective(opportunistic)
      • nipple
    • Inflammation, inflamed, inflammatory(with exudation)
      • areola
    • Inflammation, inflamed, inflammatory(with exudation)
      • breast
    • Inflammation, inflamed, inflammatory(with exudation)
      • nipple
    • Mammillitis
    • Mastitis(acute) (diffuse) (nonpuerperal) (subacute)
    • Mastitis(acute) (diffuse) (nonpuerperal) (subacute)
      • infective
    • Mastitis(acute) (diffuse) (nonpuerperal) (subacute)
      • without abscess
    • Thelitis

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 N61.0 to ICD-9-CMHistory

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

ICD-9-CM
611.0 Inflam disease of breast
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement N61.0 replaces the following previously assigned code(s):

  • N61 - Inflammatory disorders of breast
FY 2018AddedAdded to the ICD-10-CM code setEffective October 1, 2017.
FY 2019–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About N61.0Overview

Is N61.0 (Inflammatory disorders of breast) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report mastitis without abscess on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does N61.0 group to?

When mastitis without abscess 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 N61.0?

Under the General Equivalence Mappings, mastitis without abscess converts to ICD-9-CM 611.0 (inflam disease of breast). The mapping is approximate, so confirm the match fits the documentation.

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.