ICD-10 Code C84.04 – Mycosis fungoides, lymph nodes of axilla and upper limb (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C84.04 – Mycosis fungoides, lymph nodes of axilla and upper limb
What it is
C84.04 identifies mycosis fungoides involving the lymph nodes of the axilla and upper limb. Use it when the documentation specifies this cutaneous T-cell lymphoma has spread to, or is affecting, those regional nodes.
Clinical signs
Findings may include persistent skin lesions consistent with mycosis fungoides and documented enlargement or involvement of axillary or upper-extremity lymph nodes. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents mycosis fungoides with lymph node involvement limited to the axilla or upper limb. It is appropriate when pathology, imaging, or exam notes support nodal disease in that anatomic region. Check documentation if the site of nodal involvement is unclear.
Do not use for
Do not use this code for mycosis fungoides without documented lymph node involvement, or when different nodal regions are specified. Do not assume axillary nodes if the record only states generalized or unspecified lymphadenopathy.
Coding tip
Match the exact lymph node site in the chart, because ICD-10-CM distinguishes mycosis fungoides by nodal location.