2026 ICD-10-CM Diagnosis Code S21.002SUnspecified open wound of left breast, sequela
S21.002S is a billable ICD-10-CM diagnosis code for unspecified open wound of left breast, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 604 through 605. The code is exempt from POA reporting. Coders also document this condition as open wound of left breast. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Injury, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
S21.002S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Open wound of left breast
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Open wound of thorax (S21). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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 S21.002S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About S21.002SOverview
Is S21.002S (Unspecified open wound of left breast) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified open wound of left breast, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in S21.002S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the unspecified open wound of left breast itself has resolved, not the original event.
What MS-DRG does S21.002S group to?
When unspecified open wound of left breast, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 604, 605, with relative weights from 0.9160 to 1.4721 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S21.002S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for unspecified open wound of left breast, sequela on inpatient claims.
What is the ICD-9 equivalent of S21.002S?
Under the General Equivalence Mappings, unspecified open wound of left breast, sequela converts to ICD-9-CM 906.0 (lt eff opn wnd head/trnk). 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.
