C91.42
✓ Billable
Hairy cell leukemia, in relapse
ICD-10-CM · FY2026 · Neoplasms
Code
C91.42
System
ICD-10-CM
Billable
Yes — valid for submission
Effective
FY2026
Chapter
Neoplasms
Source
CMS / CDC NCHS
⚠ Verify before billing. Confirm against the current CMS/NCHS ICD-10-CM files and your payer's rules before claims submission.
Frequently asked questions
What is ICD-10 code C91.42?
ICD-10-CM code C91.42 represents Hairy cell leukemia, in relapse. It is a billable diagnosis code in the Neoplasms chapter, effective October 1, 2025 – September 30, 2026.
Is C91.42 billable?
Yes. C91.42 is a valid billable ICD-10-CM code for insurance claims and clinical documentation.
What chapter is C91.42 in?
C91.42 belongs to the Neoplasms chapter (C00–D49) of ICD-10-CM.
Related codes in the C91 category
C91
Lymphoid leukemia
Non-billable
C91.0
Acute lymphoblastic leukemia [ALL]
Non-billable
C91.1
Chronic lymphocytic leukemia of B-cell type
Non-billable
C91.3
Prolymphocytic leukemia of B-cell type
Non-billable
C91.4
Hairy cell leukemia
Non-billable
C91.5
Adult T-cell lymphoma/leukemia (HTLV-1-associated)
Non-billable
C91.6
Prolymphocytic leukemia of T-cell type
Non-billable
C91.A
Mature B-cell leukemia Burkitt-type
Non-billable
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