ICD-10 Code C91.51 – Adult T-cell lymphoma/leukemia (HTLV-1-associated), in remission (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.51 – Adult T-cell lymphoma/leukemia (HTLV-1-associated), in remission
What it is
This code identifies a history of adult T-cell lymphoma/leukemia caused by HTLV-1, when the disease is documented as in remission. Use it when the condition remains a relevant diagnosis, but active disease is not currently present.
Clinical signs
Clinical features vary; refer to documentation. Typical records may note prior T-cell lymphoma/leukemia, HTLV-1 association, and remission status confirmed by the treating clinician.
When to use this code
Use C91.51 when the provider documents adult T-cell lymphoma/leukemia as in remission and still tracks the condition for ongoing care. It may appear in follow-up oncology notes, survivorship visits, or problem lists. Confirm that remission is clearly stated and not merely implied by past history.
Do not use for
Do not use this code for active adult T-cell lymphoma/leukemia or when remission is not documented. Check documentation if the record only mentions HTLV-1 infection, past treatment, or suspected recurrence.
Coding tip
Code the remission status only when the provider explicitly documents it; otherwise, verify whether active disease or history-only coding is appropriate.