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S20.17 vs S21.051

S20.17 (Other superficial bite of breast) compared with S21.051 (Open bite of right breast), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes should not be reported together because S20.17’s tabular entry lists S21.051 under Excludes1.

Official rule
What is different?

The conditions named.S20.17 is “Other superficial bite of breast”; S21.051 is “Open bite of right breast”.

Registry fact

Can these codes be reported together?

No.S20.17’s entry carries an Excludes1 note covering S21.051: “open bite of breast (S21.05-)”. Both may be reported only when the documentation shows the two conditions are unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

Yes.S20.17’s tabular entry: “open bite of breast (S21.05-)”. The note covers S21.051.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. S20.17 carries 11 Excludes2 notes and S21.051 carries 11 Excludes2 notes covering other codes; the side-by-side table quotes them.

Official rule

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?

Both are headers.Both are non-billable headers, 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?

Excludes1 — generally not reported together

Excludes1 conflict

S20.17
Other superficial bite of breast
↔
S21.051
Open bite of right breast

What we found

No — do not report together.S20.17 carries an Excludes1 note covering S21.051: “open bite of breast (S21.05-)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

What to review

Report one of the two. Both may be reported only when the documentation shows the two conditions are unrelated to each other.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes1 note means the two conditions are not ordinarily reported together for the same encounter, because the classification treats them as mutually exclusive forms of the same condition. The documented exception is when the two conditions are unrelated to each other.

Source / rule

CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a

Official guidance behind these answers

  • Section I.A.12.a — Excludes1 · applies to: Excludes1

    A type 1 Excludes note is a pure excludes note. It means “NOT CODED HERE!” An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition. An exception to the Excludes1 definition is the circumstance when the two conditions are unrelated to each other. If it is not clear whether the two conditions involving an Excludes1 note are related or not, query the provider. For example, code F45.8, Other somatoform disorders, has an Excludes1 note for "sleep related teeth grinding (G47.63)," because "teeth grinding" is an inclusion term under F45.8. Only one of these two codes should be assigned for teeth grinding. However psychogenic dysmenorrhea is also an inclusion term under F45.8, and a patient could have both this condition and sleep related teeth grinding. In this case, the two conditions are clearly unrelated to each other, and so it would be appropriate to report F45.8 and G47.63 together.

    ICD-10-CM Official Guidelines FY2027

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

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
S20.17

Other superficial bite of breast

S21.051

Open bite of right breast

StatusDiffers
S20.17
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: S20.171A, S20.171D, S20.171S, S20.172A, S20.172D

S21.051
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: S21.051A, S21.051D, S21.051S

Excludes1Differs
S20.17
  • open bite of breast (S21.05-)
S21.051
  • superficial bite of breast (S20.17)
  • traumatic amputation (partial) of thorax (S28.1)
Excludes2Same for both
  • burns and corrosions (T20-T32)
  • effects of foreign body in bronchus (T17.5)
  • effects of foreign body in esophagus (T18.1)
  • effects of foreign body in lung (T17.8)
  • effects of foreign body in trachea (T17.4)
  • frostbite (T33-T34)
  • injuries of axilla
  • injuries of clavicle
  • injuries of scapular region
  • injuries of shoulder
  • insect bite or sting, venomous (T63.4)
Code alsoDiffers
S20.17

None at this code

S21.051
  • any associated injury, such as:
  • injury of heart (S26.-)
  • injury of intrathoracic organs (S27.-)
  • rib fracture (S22.3-, S22.4-)
  • spinal cord injury (S24.0-, S24.1-)
  • traumatic hemopneumothorax (S27.3)
  • traumatic hemothorax (S27.1)
  • traumatic pneumothorax (S27.0)
  • wound infection
CategoryDiffers
S20.17

S20 Superficial injury of thorax

S21.051

S21 Open wound of thorax

ChapterSame for both

S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)

IncludesSame for both
  • injuries of breast
  • injuries of chest (wall)
  • injuries of interscapular area
7th characterDiffers
S20.17
  • The appropriate 7th character is to be added to each code from category S20
S21.051
  • The appropriate 7th character is to be added to each code from category S21

No Code first and Use additional code note at either code.

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. In a row that differs, notes every code shares are dimmed.

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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