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ICD-10 Code C84.0: Mycosis fungoides

C84.0 is an ICD-10 diagnosis entry used to group records related to Mycosis fungoides. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).

When is it used?

  • May be used when a clinician documents mycosis fungoides in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
  • This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter
2Neoplasms (C00-D49)
block
C00-C96Malignant neoplasms
block
C81-C96Malignant neoplasms of lymphoid, hematopoietic and related tissue
category
C84Mature T/NK-cell lymphomas
currentC84

Official coding notes

Excludes1 (do not code together)
  • peripheral T-cell lymphoma, not elsewhere classified (C84.4-)

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

OncologistGeneral Physician

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.
Legacy codes
C84.0
Replacement codes
C84.00 — Mycosis fungoides, unspecified siteC84.01 — Mycosis fungoides, lymph nodes of head, face, and neckC84.02 — Mycosis fungoides, intrathoracic lymph nodesC84.03 — Mycosis fungoides, intra-abdominal lymph nodesC84.04 — Mycosis fungoides, lymph nodes of axilla and upper limbC84.05 — Mycosis fungoides, lymph nodes of inguinal region and lower limbC84.06 — Mycosis fungoides, intrapelvic lymph nodesC84.07 — Mycosis fungoides, spleenC84.08 — Mycosis fungoides, lymph nodes of multiple sitesC84.09 — Mycosis fungoides, extranodal and solid organ sitesC84.0A — Mycosis fungoides, in remission

Common synonyms

Mycosis fungoides

Frequently asked questions

Code details

CodeC84.0
SystemICD10
Display nameMycosis fungoides
ChapterNeoplasms (C00-D49)
BlockMalignant neoplasms of lymphoid, hematopoietic and related tissue

Flags

BillableNo
Valid clinical useNo

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.