ICD-10 Code C85.20 – Mediastinal (thymic) large B-cell lymphoma, unspecified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C85.20 – Mediastinal (thymic) large B-cell lymphoma, unspecified site
What it is
This code identifies a large B-cell lymphoma arising in the mediastinum, often from thymic tissue, when the site is not further specified. Use it for documentation that names mediastinal or thymic large B-cell lymphoma without a more precise location.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include a mediastinal mass with chest pressure, cough, shortness of breath, or other signs from local compression.
When to use this code
Use this code when the record clearly states mediastinal (thymic) large B-cell lymphoma and does not name a more specific site. It also fits when pathology or oncology notes confirm this subtype but the chart only supports an unspecified mediastinal location. If laterality or a different anatomic site is documented, check documentation.
Do not use for
Do not use this code for other non-Hodgkin lymphomas, Hodgkin lymphoma, or large B-cell lymphoma outside the mediastinum. Do not assign it when the record identifies a different primary site.
Coding tip
Code from the provider’s exact wording and confirm that “mediastinal” or “thymic” is documented before assigning C85.20.