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U.S. ICD-10-CM · April 2026

C91 ICD-10-CM Code: Lymphoid leukemia

A clear reference for the official code description, hierarchy, and related coding information from the April 2026 U.S. release.

Code definition

Official description

C91

Lymphoid leukemia

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where C91 sits

  1. 1

    Chapter 2

    Neoplasms (C00-D49)

  2. 2

    Section

    Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)

  3. 3

    Category C91

    Lymphoid leukemia

  4. 4

    Code C91

    Lymphoid leukemia

More specific choices

Codes under C91

C91 is a non-billable category. Choose the child code that best matches the documented diagnosis.

C91.0

Acute lymphoblastic leukemia [ALL]

C91.1

Chronic lymphocytic leukemia of B-cell type

C91.3

Prolymphocytic leukemia of B-cell type

C91.4

Hairy cell leukemia

C91.5

Adult T-cell lymphoma/leukemia (HTLV-1-associated)

C91.6

Prolymphocytic leukemia of T-cell type

C91.9

Lymphoid leukemia, unspecified

C91.A

Mature B-cell leukemia Burkitt-type

C91.Z

Other lymphoid leukemia

Documentation details

Notes for this code

Inclusion terms

No inclusion terms are listed for C91.

Code first

No “code first” instruction is listed for C91.

Use additional code

No “use additional code” instruction is listed for C91.

Excludes1

Conditions that should not be reported together with this code.

  • personal history of leukemia (Z85.6)

Excludes2

Conditions not included here that may be reported separately when present.

No Excludes2 note is listed for C91.

Transparency

Source and release

Data release

U.S. ICD-10-CM · April 2026

Effective date

Apr 1, 2026

Publisher

Vero Scribe Inc.

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code C91 mean?

C91 is the April 2026 U.S. ICD-10-CM code for “Lymphoid leukemia.”

Is C91 a billable or specific ICD-10-CM code?

No. C91 has more specific child codes in the April 2026 reference data. Select the code that matches the documentation and confirm the active code set and payer requirements.

Where is C91 located in ICD-10-CM?

C91 is listed in Chapter 2, Neoplasms (C00-D49), within Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96) (C81–C96), under category C91, Lymphoid leukemia.

What coding notes are listed for C91?

No inclusion terms are listed for C91 in this reference record. No code-first instruction is listed. Excludes1 notes: personal history of leukemia (Z85.6). No Excludes2 note is listed.

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