ICD-10 Code C91.52 – Adult T-cell lymphoma/leukemia (HTLV-1-associated), in relapse (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.52 – Adult T-cell lymphoma/leukemia (HTLV-1-associated), in relapse
What it is
This code identifies a recurrent episode of adult T-cell lymphoma/leukemia linked to HTLV-1 infection. Use it when the disease had responded or remitted and is now documented as having returned.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include lymphadenopathy, skin lesions, hepatosplenomegaly, or leukemic blood involvement, but the record should confirm relapse of the HTLV-1-associated disease.
When to use this code
Use C91.52 when the provider documents adult T-cell lymphoma/leukemia as relapsed, recurrent, or returned after prior remission. It applies to the active recurrent episode, not the initial diagnosis. If the note does not clearly state relapse, check documentation before assigning the code.
Do not use for
Do not use this code for the initial presentation of adult T-cell lymphoma/leukemia or for remission status alone. If the chart describes a different lymphoma, leukemia, or HTLV-1 condition, code the documented diagnosis instead.
Coding tip
Look for explicit wording such as “relapse,” “recurrent,” or “in recurrence” and confirm the HTLV-1 association in the assessment.