Acute undifferentiated leukemia

ICD-O-1 Morphology
Effective 1978 - 1991
ICD-O-2 Morphology
Effective 1992 - 2000
ICD-O-3 Morphology
Effective 2001 and later
for cases diagnosed 1978 and later
Primary Site(s)
Primary site must be bone marrow (C421)

Not Applicable
Module Rule
See abstractor notes
Acute undifferentiated leukemia expresses no markers considered 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, such as those derived from myeloid or plasmacytoid dendritic cell precursors, NK-cell precursors, basophils or even non-hematopoietic tumors.
Abstractor Notes
Historically the description for this code has been Acute leukemia, NOS. In the new WHO classification, the definition has been 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.
Definitive Diagnostic Methods
Bone marrow biopsy
Clinical diagnosis
Peripheral blood smear
Genetics Data
Delete TdT
Bone marrow transplant
Transformations to
There are no known transformations
Transformations from
There are no known transformations
Same Primaries
Corresponding ICD-9 Codes
208.0 Acute leukemia of unspecified cell type
Corresponding ICD-10 Codes
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)
Signs and Symptoms
Bone or joint pain
Easy bruising or bleeding
Eczema-like skin rash
Night sweats
Pain or feeling of fullness below the ribs
Painless lumps
Shortness of breath
Progression and Transformation
Epidemiology and Mortality