SEER is an authoritative source of information on cancer incidence and survival in the United States. SEER currently collects and publishes cancer incidence and survival data from population-based cancer registries covering approximately 28 percent of the U.S. population.
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.