Skip to main content

B35-B49 vs C84.0

B35-B49 (Mycoses (B35-B49)) compared with C84.0 (Mycosis fungoides), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because B35-B49 lists C84.0 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named and chapter.B35-B49 is “Mycoses (B35-B49)”; C84.0 is “Mycosis fungoides”. B35-B49 sits in A00-B99 — Certain Infectious and Parasitic Diseases (A00-B99); C84.0 in C00-D49 — Neoplasms (C00-D49).

Registry fact

Can these codes be reported together?

Yes, when both are documented.B35-B49 lists C84.0 under Excludes2: “mycosis fungoides (C84.0-)”. 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. C84.0 carries 2 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.B35-B49’s tabular entry: “mycosis fungoides (C84.0-)”. The note covers C84.0.

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?

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?

Informational

Excludes2 relationship

B35-B49
Mycoses (B35-B49)
↔
C84.0
Mycosis fungoides

What we found

Yes, when both are documented.B35-B49 carries an Excludes2 note covering C84.0: “mycosis fungoides (C84.0-)”

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

B35-B49Mycoses (B35-B49)C84.0Mycosis fungoides
Billing statusNon-billable headerNon-billable header

Report instead: C84.00, C84.01, C84.02, C84.03, C84.04

ClassificationA00-B99 — Certain Infectious and Parasitic Diseases (A00-B99)C00-D49 — Neoplasms (C00-D49)
DefinitionMycoses (B35-B49) is a non-billable ICD-10-CM category code (B35-B49).Mycosis fungoides is a non-billable ICD-10-CM category code (C84.0).
Excludes1—
peripheral T-cell lymphoma, not elsewhere classified (C84.4-)
personal history of non-Hodgkin lymphoma (Z85.72)
Excludes2
hypersensitivity pneumonitis due to organic dust (J67.-)
mycosis fungoides (C84.0-)
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