ICD-10 Code C84.12 – Sézary disease, intrathoracic lymph nodes (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C84.12 – Sézary disease, intrathoracic lymph nodes
What it is
C84.12 identifies Sézary disease involving intrathoracic lymph nodes. Use it when the record documents this cutaneous T-cell lymphoma with spread to lymph nodes inside the chest.
Clinical signs
Typical findings include generalized skin redness, itching, and abnormal circulating T cells consistent with Sézary syndrome. Intrathoracic lymph node involvement must be documented; clinical features vary, so refer to documentation.
When to use this code
Use this code when the provider specifically states Sézary disease with intrathoracic lymph node involvement. It may appear in oncology, dermatology, or pathology documentation when staging or site-specific reporting is needed.
If the note only says Sézary syndrome without a nodal site, do not assume C84.12. Check documentation for the exact anatomic location before assigning the code.
Do not use for
Do not use this code for unspecified Sézary disease or for other cutaneous T-cell lymphomas. Also avoid it when intrathoracic lymph node involvement is not documented.
Coding tip
Confirm both the Sézary diagnosis and the intrathoracic nodal site in the same record before coding C84.12.