ICD-10 Code C84.0 – Mycosis fungoides (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C84.0 – Mycosis fungoides
What it is
Mycosis fungoides is a type of cutaneous T-cell lymphoma that primarily affects the skin. Use this code when documentation identifies this specific lymphoma subtype.
Clinical signs
Common findings include persistent patches, plaques, or tumors on the skin, often with itching or scaling. Clinical features vary; refer to documentation.
When to use this code
Use C84.0 when the provider documents mycosis fungoides, Sézary syndrome is not the diagnosis, and the condition is being coded as a confirmed lymphoma. It may also apply when pathology or specialist notes clearly identify this entity. Check documentation if the record only says “cutaneous lymphoma” or “T-cell lymphoma.”
Do not use for
Do not use this code for Sézary syndrome or for nonspecific skin eruptions without a confirmed diagnosis. If the chart only suggests lymphoma without confirmation, check documentation.
Coding tip
Code the exact lymphoma subtype documented, and verify whether the note distinguishes mycosis fungoides from other cutaneous T-cell lymphomas.