ICD-10 Code C91.Z2 – Other lymphoid leukemia, in relapse (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.Z2 – Other lymphoid leukemia, in relapse
What it is
This code identifies a relapse of a lymphoid leukemia that does not fit a more specific ICD-10 category. Use it when the record clearly states the leukemia has returned after prior remission or response.
Clinical signs
Clinical features vary; refer to documentation. Relapse is usually supported by evidence of recurrent disease in marrow, blood, or other involved sites, along with a clinician’s diagnosis of recurrent lymphoid leukemia.
When to use this code
Use C91.Z2 when the provider documents “relapse,” “recurrent,” or a similar term for other lymphoid leukemia. It applies after a prior treated episode, when the current encounter is for the return of disease. Check documentation if the leukemia type is not clearly specified.
Do not use for
Do not use this code for newly diagnosed lymphoid leukemia, remission status, or unspecified leukemia without relapse. If the record names a more specific lymphoid leukemia category, code that diagnosis instead.
Coding tip
Link the code to explicit provider wording about relapse and confirm the leukemia subtype is not better captured elsewhere.