2026 ICD-10-CM Diagnosis Code C84.00Mycosis fungoides, unspecified site

ICD-10-CM Codes›C00–D49›C81-C96›C84

ICD-10-CM C84.00
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C84.00 is a billable ICD-10-CM diagnosis code for mycosis fungoides, unspecified site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 820 through 825, 840 through 842. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Non-Hodgkin lymphoma.

Code Identity

ICD-10-CM Code
C84.00
Billable Status
Yes — Valid for Submission
Code Describes
Mycosis fungoides, unspecified site
Short Description
Mycosis fungoides, unspecified site
Same as the full description in the CMS dataset.
Parent Code
C84.0
Mycosis fungoides

Code Classification

ChapterC00–D49Neoplasms
SectionC81-C96Malignant neoplasms of lymphoid, hematopoietic and related tissue
CategoryC84Mature T/NK-cell lymphomas
This CodeC84.00Mycosis fungoides, unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bullous mycosis fungoides
  • Classic mycosis fungoides
  • Follicular mucinosis type mycosis fungoides
  • Generalized pagetoid reticulosis
  • Granulomatous mycosis fungoides
  • Localized pagetoid reticulosis
  • Lymphomatoid papulosis-associated mycosis fungoides
  • Mycosis fungoides
  • Pagetoid reticulosis
  • Patch/plaque stage mycosis fungoides
  • Poikilodermatous mycosis fungoides
  • Secondary catabolic mucinosis of skin
  • Spongiotic mycosis fungoides
  • Syringotropic mycosis fungoides
  • Tumor stage mycosis fungoides

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO058
Non-Hodgkin lymphoma
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Mycosis Fungoides

    a chronic, malignant t-cell lymphoma of the skin. in the late stages, the lymph nodes and viscera are affected.

  • Pagetoid Reticulosis

    a distinct variant of mycosis fungoides characterized by the presence of localized patches or plaques with an intraepidermal proliferation of neoplastic cells.

  • Lymph Nodes

    they are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system.

Patient EducationClinical

Lymphoma

Lymphoma is a cancer of a part of the immune system called the lymph system. There are many types of lymphoma. One type is Hodgkin disease. The rest are called non-Hodgkin lymphomas.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C84.00 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
202.10 Mycs fng unsp xtrndl org
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C84.00Overview

Is C84.00 (Mycosis fungoides) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report mycosis fungoides, unspecified site on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C84.00 group to?

When mycosis fungoides, unspecified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 820, 821, 822, 823, 824, 825, 840, 841, 842, with relative weights from 1.0104 to 5.8648 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C84.00?

Under the General Equivalence Mappings, mycosis fungoides, unspecified site converts to ICD-9-CM 202.10 (mycs fng unsp xtrndl org). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.