2025 ICD-10-CM Diagnosis Code C91.4

by

Hairy cell leukemia

  • C91.4 should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.
  • The 2025 edition of ICD-10-CM C91.4 became effective on October 1, 2024.
  • This is the American ICD-10-CM version of C91.4 – other international versions of ICD-10 C91.4 may differ.

Applicable To

  • Leukemic reticuloendotheliosis

The following code(s) above C91.4 contain annotation back-references

 that may be applicable to C91.4:

  • C00-D49  Neoplasms
  • C81-C96  Malignant neoplasms of lymphoid, hematopoietic and related tissue
  • C91  Lymphoid leukemia

Clinical Information

  • A neoplastic disease of the lymphoreticular cells which is considered to be a rare type of chronic leukemia; it is characterized by an insidious onset, splenomegaly, anemia, granulocytopenia, thrombocytopenia, little or no lymphadenopathy, and the presence of “hairy” or “flagellated” cells in the blood and bone marrow.
  • A rare neoplasm of small b-lymphocytes with “hairy” projections in bone marrow, spleen, and peripheral blood. Most patients are middle-aged to elderly adults and present with splenomegaly and pancytopenia. (who, 2001)
  • A rare type of leukemia in which abnormal b-lymphocytes (a type of white blood cell) are present in the bone marrow, spleen, and peripheral blood. When viewed under a microscope, these cells appear to be covered with tiny hair-like projections.
  • Neoplastic disease of the lymphoreticular cells which is considered to be a rare type of chronic leukemia; it is characterized by an insidious onset, splenomegaly, anemia, granulocytopenia, thrombocytopenia, little or no lymphadenopathy, and the presence of hairy or flagellated cells in the blood and bone marrow.

Code History

  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
  • 2022 (effective 10/1/2021): No change
  • 2023 (effective 10/1/2022): No change
  • 2024 (effective 10/1/2023): No change
  • 2025 (effective 10/1/2024): No change

Code annotations containing back-references to C91.4:

Diagnosis Index entries containing back-references to C91.4:

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