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Name
Acute undifferentiated leukemia
ICD-O-3 Morphology
Effective
2001 and later
Reportable
for cases diagnosed
1978 and later
Primary Site(s)
C421
Primary site must be bone marrow (C421)
Coding Manual:
Hematopoietic Coding Manual (PDF)
Abstractor Notes
Acute undifferentiated leukemia is part of the Acute leukemias of mixed or ambiguous lineage table in the WHO 5th edition of Hematolymphoid Tumors. (See Appendix B in the Hematopoietic Manual, Table B9)
Historically the description for this code has been Acute leukemia, NOS. In the 2008 WHO classification, the definition was changed to acute undifferentiated leukemia.
Acute leukemia NOS is a generic disease description. DCO cases or path report only cases may stay in this classification. In most cases, leukemia, NOS is only the provisional diagnosis; the physician will run further diagnostic procedures and look for various clinical presentations to identify a more specific disease.
Further review of the medical record should be done to look for the tests listed as definitive diagnosis. If no information is found on the medical record, follow-back with the attending physician must be done. The more specific leukemias are any of the specific acute leukemias. When a more specific diagnosis is identified, the histology should be changed to the more specific neoplasm name and code. See the histology tables for more information on NOS and more specific histologies.
Acute undifferentiated leukemia affects the bone marrow and peripheral blood. There are too few cases to know whether there is a predilection for other sites. These leukemias are very rare and nothing substantial is known about their frequency. While anecdotal experience generally considers these leukemias to be of poor prognosis, information is too scanty to make any definitive statements.
Historically the description for this code has been Acute leukemia, NOS. In the 2008 WHO classification, the definition was changed to acute undifferentiated leukemia.
Acute leukemia NOS is a generic disease description. DCO cases or path report only cases may stay in this classification. In most cases, leukemia, NOS is only the provisional diagnosis; the physician will run further diagnostic procedures and look for various clinical presentations to identify a more specific disease.
Further review of the medical record should be done to look for the tests listed as definitive diagnosis. If no information is found on the medical record, follow-back with the attending physician must be done. The more specific leukemias are any of the specific acute leukemias. When a more specific diagnosis is identified, the histology should be changed to the more specific neoplasm name and code. See the histology tables for more information on NOS and more specific histologies.
Acute undifferentiated leukemia affects the bone marrow and peripheral blood. There are too few cases to know whether there is a predilection for other sites. These leukemias are very rare and nothing substantial is known about their frequency. While anecdotal experience generally considers these leukemias to be of poor prognosis, information is too scanty to make any definitive statements.
Diagnostic Confirmation
This histology can be determined by positive histology (including peripheral blood) with or without genetics and/or immunophenotyping. Review the Definitive Diagnostic Methods, Immunophenotyping and Genetics Data sections below, and the instructions in the Hematopoietic Manual for further guidance on assigning Diagnostic confirmation.
Module Rule
See abstractor notes
Alternate Names
Definition
Acute undifferentiated leukemia expresses no markers that are specific for either lymphoid or myeloid lineage. Before categorizing a leukemia as undifferentiated, it is necessary to perform immunophenotyping with a comprehensive panel of monoclonal antibodies in order to exclude leukemias of unusual lineages.
Definitive Diagnostic Methods
Clinical diagnosis
Cytogenetics
Histologic confirmation
Immunohistochemistry
Immunophenotyping
Genetics Data
None
Immunophenotyping
CD34 weakly expressed or positive
CD38 expression
HLA-DR expression
TdT positive
Treatments
Chemotherapy
Hematologic Transplant and/or Endocrine Procedures
Transformations to
There are no known transformations
Transformations from
There are no known transformations
Same Primaries
Corresponding ICD-10 Codes (Cause of Death codes only)
C95.0 Acute leukemia of unspecified cell type
Corresponding ICD-10-CM Codes (U.S. only)
C95.0 Acute leukemia of unspecified cell type (effective October 01, 2015 - September 30, 2024)
C95.00 Acute leukemia of unspecified cell type not having achieved remission (effective October 01, 2024)
C95.01 Acute leukemia of unspecified cell type, in remission (effective October 01, 2024)
C95.02 Acute leukemia of unspecified cell type, in relapse (effective October 01, 2024)
Signs and Symptoms
Diagnostic Exams
Progression and Transformation
None
Epidemiology and Mortality
None
Sources
WHO Classification of Tumours Editorial Board. Haematolymphoid tumours. Lyon (France): International Agency for Research on Cancer; 2024. (WHO classification of tumours series, 5th ed.; vol. 11). https://publications.iarc.who.int/637.
Section: Acute leukemias of mixed or ambiguous lineage
Pages: Part A: 219-220
Section: Acute leukemias of mixed or ambiguous lineage
Pages: Part A: 219-220
International Classification of Diseases for Oncology, 3rd edition (including revisions). Geneva: World Health Organization, 2001, 2011, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes
Pages: http://www.iacr.com.fr/index.php?option=com_content&view=category&layout=blog&id=100&Itemid=577
Section: ICD-O-3.2 (2020) Morphological Codes
Pages: http://www.iacr.com.fr/index.php?option=com_content&view=category&layout=blog&id=100&Itemid=577
