ICD-10 Code C86.4 – Blastic NK-cell lymphoma (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C86.4 – Blastic NK-cell lymphoma
What it is
C86.4 identifies blastic NK-cell lymphoma, a rare and aggressive lymphoma of natural killer-cell lineage. Use it when the record specifically documents this diagnosis.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include rapidly enlarging skin lesions, lymphadenopathy, and bone marrow or systemic involvement.
When to use this code
Use C86.4 when the clinician documents blastic NK-cell lymphoma as the confirmed diagnosis. It may also apply when pathology or oncology notes clearly state this entity, even if the site of involvement is still being worked up.
If the chart only says “NK-cell lymphoma” or another lymphoma subtype, check documentation before assigning this code. Code the most specific diagnosis supported by the record.
Do not use for
Do not use this code for other mature T/NK-cell lymphomas, unspecified lymphoma, or suspected disease without confirmation. Check documentation if the pathology report does not clearly name blastic NK-cell lymphoma.
Coding tip
Assign C86.4 only when the exact lymphoma type is documented; otherwise, query for clarification.