2027 ICD-10-CM Diagnosis Code N64.1Fat necrosis of breast

ICD-10-CM Codes›N00–N99›N60-N65›N64

ICD-10-CM N64.1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

N64.1 is a billable ICD-10-CM diagnosis code for fat necrosis of breast. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 600 through 601. The code is not accepted as a principal diagnosis by the Medicare Code Editor. Coders also document this condition as bilateral fat necrosis of breasts. 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
N64.1
Billable Status
Yes — Valid for Submission
Code Describes
Fat necrosis of breast
Short Description
Fat necrosis of breast
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 CodeN64.1Fat necrosis of breast

Code EditsBilling

Medicare Code Editor checks that affect claim validity for N64.1.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bilateral fat necrosis of breasts
  • Fat necrosis of breast
  • Fat necrosis of left breast
  • Fat necrosis of right breast

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to N64.1: its own notes plus those printed at N64, block N60-N65, and Chapter 14. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Fat necrosis (segmental) of breast

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block N60-N65 Disorders of breast applies to 60 codes
  • disorders of breast associated with childbirth (O91-O92)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From N64 Other disorders of breast applies to 13 codes
  • mechanical complication of breast prosthesis and implant (T85.4-)
From Chapter 14 (N00-N99) Diseases of the genitourinary system applies to 838 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Code First

The underlying condition named in the note is sequenced before this code.

  • breast necrosis due to breast graft (T85.898)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR GEN017
Nonmalignant breast conditions
Default principal diagnosis: inpatient No · outpatient Yes

Clinical InformationClinical

  • Breast Fat Necrosis

    localized necrosis of the adipose tissue in the breast. clinically, it may present as a mass. causes include injury, surgical procedures, and radiation treatment.

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 N64.1 to ICD-9-CMHistory

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

ICD-9-CM
611.3 Fat necrosis of breast
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About N64.1Overview

What is the ICD-10 code for fat necrosis of breast?

The ICD-10-CM code for fat necrosis of breast is N64.1 (sometimes written as N641). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is N64.1 (Other disorders of breast) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fat necrosis of breast on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does N64.1 group to?

On inpatient claims, fat necrosis of breast maps to MS-DRG 600, 601, with relative weights from 0.6014 to 0.9971 depending on complications. Higher weights mean higher Medicare reimbursement.

Can N64.1 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because fat necrosis of breast describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

What is coded first with N64.1?

The Code First note reads: breast necrosis due to breast graft (T85.898). When one of these applies, it is sequenced before N64.1.