2026 ICD-10-CM Diagnosis Code N63.21Unspecified lump in the left breast, upper outer quadrant

ICD-10-CM Codes›N00–N99›N60-N65›N63

ICD-10-CM N63.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N63.21 is a billable ICD-10-CM diagnosis code for unspecified lump in the left breast, upper outer quadrant. 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 lump in upper outer quadrant of left breast. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nonmalignant breast conditions.

Code Identity

ICD-10-CM Code
N63.21
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified lump in the left breast, upper outer quadrant
Short Description
Unspecified lump in the left breast, upper outer quadrant
Same as the full description in the CMS dataset.
Parent Code
N63.2
Unspecified lump in the left breast

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN60-N65Disorders of breast
CategoryN63Unspecified lump in breast
This CodeN63.21Unspecified lump in the left breast, upper outer quadrant

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Lump in upper outer quadrant of left breast

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.

    • Lump
      • breast
        • left
          • upper outer quadrant

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 N63.21 to ICD-9-CMHistory

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

ICD-9-CM
611.72 Lump or mass in breast
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement N63.21 replaces the following previously assigned code(s):

  • N63 - Unspecified lump in 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 N63.21Overview

Is N63.21 (Unspecified lump in the left breast) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified lump in the left breast, upper outer quadrant on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does N63.21 group to?

When unspecified lump in the left breast, upper outer quadrant 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 N63.21?

Under the General Equivalence Mappings, unspecified lump in the left breast, upper outer quadrant converts to ICD-9-CM 611.72 (lump or mass in 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.