ICD-10 Code C91.9 – Lymphoid leukemia, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.9 – Lymphoid leukemia, unspecified
What it is
This code identifies a leukemia of lymphoid cell origin when the record does not specify the exact subtype. Use it when documentation confirms lymphoid leukemia but does not name the specific form.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings may include fatigue, infections, bruising, lymphadenopathy, or abnormal blood counts, but you should code only what is documented.
When to use this code
Use C91.9 when the provider documents lymphoid leukemia without further detail, such as in an initial note, problem list, or referral summary. It is also appropriate when the subtype is not yet established after evaluation. If later documentation identifies a specific leukemia type, update the code accordingly.
Do not use for
Do not use this code for a clearly specified lymphoid leukemia subtype, such as acute or chronic forms, when documentation supports a more precise code. Do not use it for non-lymphoid leukemias or for a history of leukemia only.
Coding tip
Query for the exact leukemia subtype whenever the record says only “lymphoid leukemia” or “leukemia” without clarification.