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N64.4 vs R23.4

N64.4 (Mastodynia) compared with R23.4 (Changes in skin texture), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because R23.4 lists N64.4 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named and chapter.N64.4 is “Mastodynia”; R23.4 is “Changes in skin texture”. N64.4 sits in N00-N99 — Diseases of the Genitourinary System (N00-N99); R23.4 in R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99).

Registry fact

Can these codes be reported together?

Yes, when both are documented.R23.4 lists N64.4 under Excludes2: “symptoms relating to breast (N64.4-N64.5)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. N64.4 carries 1 Excludes1 note and R23.4 carries 1 Excludes1 note covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.R23.4’s tabular entry: “symptoms relating to breast (N64.4-N64.5)”. The note covers N64.4.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

No.Both are billable codes, and neither contains the other.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

R23.4
Changes in skin texture
↔
N64.4
Mastodynia

What we found

Yes, when both are documented.R23.4 carries an Excludes2 note covering N64.4: “symptoms relating to breast (N64.4-N64.5)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2026

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

N64.4MastodyniaR23.4Changes in skin texture
Billing statusBillableBillable
ClassificationN00-N99 — Diseases of the Genitourinary System (N00-N99)R00-R99 — Symptoms, Signs and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99)
DefinitionMastodynia is a billable ICD-10-CM diagnosis code (N64.4).Changes in skin texture is a billable ICD-10-CM diagnosis code (R23.4).
Includes—
Desquamation of skin
Induration of skin
Scaling of skin
Excludes1
disorders of breast associated with childbirth (O91-O92)
epidermal thickening NOS (L85.9)
Excludes2
mechanical complication of breast prosthesis and implant (T85.4-)
symptoms relating to breast (N64.4-N64.5)

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

Edit this comparisonCheck a whole claim

Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources