2025 ICD-10-CM Diagnosis Code C91.40

Hairy cell leukemia not having achieved remission

  • C91.40 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • The 2025 edition of ICD-10-CM C91.40 became effective on October 1, 2024.
  • This is the American ICD-10-CM version of C91.40 – other international versions of ICD-10 C91.40 may differ.

Applicable To

  • Hairy cell leukemia with failed remission
  • Hairy cell leukemia NOS

The following code(s) above C91.40 contain annotation back-references

 that may be applicable to C91.40:

  • C00-D49  Neoplasms
  • C81-C96  Malignant neoplasms of lymphoid, hematopoietic and related tissue
  • C91  Lymphoid leukemia
  • C91.4  Hairy cell leukemia

Approximate Synonyms

  • Hairy cell leukemia (clinical)
  • Hairy cell leukemia, arm ln
  • Hairy cell leukemia, axillary ln
  • Hairy cell leukemia, head ln
  • Hairy cell leukemia, inguinal ln
  • Hairy cell leukemia, leg ln
  • Hairy cell leukemia, neck ln
  • Leukemia, hairy cell
  • Leukemic reticuloendotheliosis
  • Leukemic reticuloendotheliosis extranod or solitar
  • Leukemic reticuloendotheliosis intrapelvic lymph n
  • Leukemic reticuloendotheliosis of extranodal and/or solid organ site
  • Leukemic reticuloendotheliosis of intra-abdominal lymph nodes
  • Leukemic reticuloendotheliosis of intrapelvic lymph nodes
  • Leukemic reticuloendotheliosis of intrathoracic lymph nodes
  • Leukemic reticuloendotheliosis of lymph nodes of axilla
  • Leukemic reticuloendotheliosis of lymph nodes of head
  • Leukemic reticuloendotheliosis of lymph nodes of inguinal region
  • Leukemic reticuloendotheliosis of lymph nodes of lower limb
  • Leukemic reticuloendotheliosis of lymph nodes of multiple sites
  • Leukemic reticuloendotheliosis of lymph nodes of neck
  • Leukemic reticuloendotheliosis of lymph nodes of upper limb
  • Leukemic reticuloendotheliosis of spleen
  • Leukemic reticuloendotheliosis spleen

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.

ICD-10-CM C91.40 is grouped within Diagnostic Related Group(s) (MS-DRG v42.0):

  • 011 Tracheostomy for face, mouth and neck diagnoses or laryngectomy with mcc
  • 012 Tracheostomy for face, mouth and neck diagnoses or laryngectomy with cc
  • 013 Tracheostomy for face, mouth and neck diagnoses or laryngectomy without cc/mcc
  • 820 Lymphoma and leukemia with major o.r. Procedures with mcc
  • 821 Lymphoma and leukemia with major o.r. Procedures with cc
  • 822 Lymphoma and leukemia with major o.r. Procedures without cc/mcc
  • 823 Lymphoma and non-acute leukemia with other procedures with mcc
  • 824 Lymphoma and non-acute leukemia with other procedures with cc
  • 825 Lymphoma and non-acute leukemia with other procedures without cc/mcc
  • 840 Lymphoma and non-acute leukemia with mcc
  • 841 Lymphoma and non-acute leukemia with cc
  • 842 Lymphoma and non-acute leukemia without cc/mcc

Convert C91.40 to ICD-9-CMCode 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
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