2026 ICD-10-CM Diagnosis Code C91.12Chronic lymphocytic leukemia of B-cell type in relapse

ICD-10-CM Codes›C00–D49›C81-C96›C91

ICD-10-CM C91.12
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C91.12 is a billable ICD-10-CM diagnosis code for chronic lymphocytic leukemia of B-cell type in relapse. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 820 through 825, 840 through 842. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Leukemia - chronic lymphocytic leukemia (CLL).

Code Identity

ICD-10-CM Code
C91.12
Billable Status
Yes — Valid for Submission
Code Describes
Chronic lymphocytic leukemia of B-cell type in relapse
Short Description
Chronic lymphocytic leukemia of B-cell type in relapse
Same as the full description in the CMS dataset.
Parent Code
C91.1
Chronic lymphocytic leukemia of B-cell type

Code Classification

ChapterC00–D49Neoplasms
SectionC81-C96Malignant neoplasms of lymphoid, hematopoietic and related tissue
CategoryC91Lymphoid leukemia
This CodeC91.12Chronic lymphocytic leukemia of B-cell type in relapse

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO061
Leukemia - chronic lymphocytic leukemia (CLL)
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Chronic Lymphocytic Leukemia

Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells which will develop into white blood cells, red blood cells, and platelets. Each type of cell has a different job:

The full article covers:

  • What is leukemia?
  • What is chronic lymphocytic leukemia (CLL)?
  • What causes chronic lymphocytic leukemia (CLL)?
  • Who is at risk for chronic lymphocytic leukemia (CLL)?
  • What are the symptoms of chronic lymphocytic leukemia (CLL)?
  • How is chronic lymphocytic leukemia (CLL) diagnosed?
  • What are the treatments for chronic lymphocytic leukemia (CLL)?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert C91.12 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
204.12 Chr lymp leuk in relapse
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C91.12Overview

Is C91.12 (Chronic lymphocytic leukemia of B-cell type) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chronic lymphocytic leukemia of B-cell type in relapse on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does C91.12 group to?

When chronic lymphocytic leukemia of B-cell type in relapse is the principal diagnosis on an inpatient stay, it groups to MS-DRG 820, 821, 822, 823, 824, 825, 840, 841, 842, with relative weights from 1.0104 to 5.8648 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of C91.12?

Under the General Equivalence Mappings, chronic lymphocytic leukemia of B-cell type in relapse converts to ICD-9-CM 204.12 (chr lymp leuk in relapse). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.