ICD-10 Code C91.02 – Acute lymphoblastic leukemia, in relapse (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.02 – Acute lymphoblastic leukemia, in relapse
What it is
C91.02 identifies acute lymphoblastic leukemia that has returned after a period of remission. Use it when documentation clearly states relapse or recurrent ALL.
Clinical signs
Clinical features vary; refer to documentation. Relapse may be noted by recurrent marrow involvement, circulating blasts, or renewed symptoms of leukemia such as fatigue, infections, bruising, or bleeding.
When to use this code
Use this code when the provider documents acute lymphoblastic leukemia as “in relapse,” “recurrent,” or equivalent wording. It applies after prior remission and when the current encounter is for active relapsed disease. Check the record for site or lineage details if they are specified.
Do not use for
Do not use C91.02 for newly diagnosed ALL, remission status, or history of leukemia without current relapse. If the documentation is unclear, check documentation rather than assuming relapse.
Coding tip
Confirm that the chart states relapse, because recurrence language supports C91.02 only when active disease is documented.