ICD-10 Code C91.4: Hairy cell leukemia

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Neoplasms (C00-D49).

When is it used?

• May be used when a clinician documents hairy cell leukemia in a patient's medical record.
• May appear in hospital records, claims, referrals, and clinical documentation.
• This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

• A code alone does not explain severity, treatment plan, or outcome.
• A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
• This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

Official coding notes

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

Related codes

Sibling codes

Mapped diagnoses and classifications

Coding guidelines

Compatibility

Common synonyms

Frequently asked questions