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C79.52 vs C94.3

C79.52 (Secondary malignant neoplasm of bone marrow) compared with C94.3 (Mast cell leukemia), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because C94.3 lists C79.52 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named and billing status.C79.52 is “Secondary malignant neoplasm of bone marrow”; C94.3 is “Mast cell leukemia”. C94.3 is a non-billable header; C79.52 is billable.

Registry fact

Can these codes be reported together?

Yes, when both are documented.C94.3 lists C79.52 under Excludes2: “secondary neoplasm of bone marrow (C79.52)”. 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. C79.52 carries 3 Excludes1 notes and C94.3 carries 4 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.C94.3’s tabular entry: “secondary neoplasm of bone marrow (C79.52)”. The note covers C79.52.

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?

One is a header.C94.3 is a non-billable header, but C79.52 is not one of its subdivisions.

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

C94.3
Mast cell leukemia
↔
C79.52
Secondary malignant neoplasm of bone marrow

What we found

Yes, when both are documented.C94.3 carries an Excludes2 note covering C79.52: “secondary neoplasm of bone marrow (C79.52)”

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

C79.52Secondary malignant neoplasm of bone marrowC94.3Mast cell leukemia
Billing statusBillableNon-billable header

Report instead: C94.30, C94.31, C94.32

ClassificationC00-D49 — Neoplasms (C00-D49)C00-D49 — Neoplasms (C00-D49)
DefinitionSecondary malignant neoplasm of bone marrow is a billable ICD-10-CM diagnosis code (C79.52).Mast cell leukemia is a non-billable ICD-10-CM category code (C94.3).
Excludes1
secondary carcinoid tumors of bone (C7B.03)
secondary carcinoid tumors (C7B.-)
secondary neuroendocrine tumors (C7B.-)
leukemic reticuloendotheliosis (C91.4-)
myelodysplastic syndromes (D46.-)
personal history of leukemia (Z85.6)
plasma cell leukemia (C90.1-)
Excludes2—
Kaposi's sarcoma of lymph nodes (C46.3)
secondary and unspecified neoplasm of lymph nodes (C77.-)
secondary neoplasm of bone marrow (C79.52)
secondary neoplasm of spleen (C78.89)

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