2026 ICD-10-CM Diagnosis Code C91.31Prolymphocytic leukemia of B-cell type, in remission

ICD-10-CM Codes›C00–D49›C81-C96›C91

ICD-10-CM C91.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C91.31 is a billable ICD-10-CM diagnosis code for prolymphocytic leukemia of B-cell type, in remission. 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. Coders also document this condition as b-cell prolymphocytic leukemia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Leukemia in remission.

Code Identity

ICD-10-CM Code
C91.31
Billable Status
Yes — Valid for Submission
Code Describes
Prolymphocytic leukemia of B-cell type, in remission
Short Description
Prolymphocytic leukemia of B-cell type, in remission
Same as the full description in the CMS dataset.
Parent Code
C91.3
Prolymphocytic leukemia of B-cell type

Code Classification

ChapterC00–D49Neoplasms
SectionC81-C96Malignant neoplasms of lymphoid, hematopoietic and related tissue
CategoryC91Lymphoid leukemia
This CodeC91.31Prolymphocytic leukemia of B-cell type, in remission

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • B-cell prolymphocytic leukemia
  • B-cell prolymphocytic leukemia in remission
  • Chronic lymphoid leukemia in remission
  • Lymphoid leukemia in remission
  • Prolymphocytic leukemia

Clinical ClassificationClinical

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

CCSR NEO075
Leukemia in remission
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 C91.31 to ICD-9-CMHistory

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

ICD-9-CM
204.81 Oth lym leuk w rmsion
Approximate The match is approximate rather than exact.

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 C91.31Overview

Is C91.31 (Prolymphocytic leukemia of B-cell type) a billable code?

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

What MS-DRG does C91.31 group to?

When prolymphocytic leukemia of B-cell type, in remission 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 C91.31?

Under the General Equivalence Mappings, prolymphocytic leukemia of B-cell type, in remission converts to ICD-9-CM 204.81 (oth lym leuk w rmsion). The mapping is approximate, so confirm the match fits the documentation.

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.