ICD-10-CM 2027
ICD-10 code for CLL (chronic lymphocytic leukemia of B-cell type)
Chronic lymphocytic leukemia of B-cell type not having achieved remission
Confirmed by the official ICD-10-CM index entry “leukemia, leukemic › chronic lymphocytic, of b-cell type”. Page updated September 29, 2026.
About coding CLL
The ICD-10-CM code for CLL (chronic lymphocytic leukemia of B-cell type) is C91.10 (Chronic lymphocytic leukemia of B-cell type not having achieved remission). The official index lists 2 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on C91.10.
It is also searched as chronic lymphocytic leukemia.
Within C91.1 (chronic lymphocytic leukemia of B-cell type), C91.10 is specifically for chronic lymphocytic leukemia of B-cell type not having achieved remission. Related codes cover in remission (C91.11) and in relapse (C91.12).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 820 (Lymphoma and Leukemia with Major O.R. Procedures with MCC, relative weight 6.2481), DRG 821 (Lymphoma and Leukemia with Major O.R. Procedures with CC, relative weight 2.2023), DRG 822 (Lymphoma and Leukemia with Major O.R. Procedures without CC/MCC, relative weight 1.1272), DRG 823 (Lymphoma and Non-Acute Leukemia with Other Procedures with MCC, relative weight 4.6059), DRG 824 (Lymphoma and Non-Acute Leukemia with Other Procedures with CC, relative weight 2.2515), DRG 825 (Lymphoma and Non-Acute Leukemia with Other Procedures without CC/MCC, relative weight 1.2995) and 3 more, in MDC 17 (Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Related CLL codes
Common questions about CLL ICD-10 codes
What is the ICD-10 code for CLL?
- C91.10 — Chronic lymphocytic leukemia of B-cell type not having achieved remission. More specific codes apply when the documentation supports them: C91.11, C91.12.
What is the ICD-10 code for chronic lymphocytic leukemia of b-cell type in remission?
- C91.11 — Chronic lymphocytic leukemia of B-cell type in remission.
What is the ICD-10 code for chronic lymphocytic leukemia of b-cell type in relapse?
- C91.12 — Chronic lymphocytic leukemia of B-cell type in relapse.
Is C91.10 billable?
- Yes. C91.10 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can C91.10 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict C91.10 as a principal diagnosis.
Is C91.10 a CC or MCC?
- C91.10 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.