Institute of Genomic Medicine
Non-Random Chromosomal Abnormalities in Hematological Malignancies
Chromosomal abnormalities in hematological malignancies are strongly correlated with tumor type and may play a role in earliest stages of tumor initiation. In the clinical setting, cytogenetic analysis has proven to be an invaluable tool in the diagnosis, prognosis, and management of hematologic malignancies.
HEMATOLOGICAL MALIGNANCIES TESTED:
- Acute Myeloid Leukemia (AML)
- The Myelodysplastic Syndromes (MDS)
- Myeloproliferative Disorders (MPD)
- Acute Lymphoblastic Leukemia (ALL)
- The Lymphomas: Burkitt's lymphoma, Hodgkin's disease, non-Hodgkin's non-Burkitt's lymphomas.
- Lymphoproliferative Disorders (LPD): B - and T-lineage disorders.
SAMPLE REQUIREMENTS:
Bone marrow is the tissue of choice for cytogenetic analysis. Exceptions to this are chronic granulocytic leukemia (CGL) and chronic lymphocytic leukemia (CLL),where a blood sample may yield specific information, and the lymphomas, best studied from a lymph node biopsy. Peripheral blood is of use only when the white blood cell count is higher than 10,000 WBC/ml and at least 10% blasts are present.
One ml of first drawn cellular bone marrow aspirate, before dilution with blood, is best. Alternatively, 5 ml of peripheral blood can be drawn if blasts are present.
SPECIMEN HANDLING:
Collect bone marrow directly into green top tube containing sodium heparin. Invert the tube several times to prevent clotting. Alternatively, collect bone marrow into a syringe containing preservative free heparin at a concentration of 1000 U/ml. Do not transfer to a green top tube if heparinized syringe is used. If a delay before sending the sample is anticipated, transfer to a sterile container with culture media such as RPMI 1640. The media is also available from the laboratory. Specimens can be stored in the media at 4℃ overnight or up to three days. Specimens can also be mailed by overnight courier. However, some deterioration occurs with storage.
PROCEDURE:
The short term culture method is used for the majority of specimens. Bone marrow is set up in culture media without the mitotic stimulant phytohemagglutinin (PHA), and incubated for 24 hrs at 370C. Ethidium bromide is used simultaneously with colcemid to improve chromosome morphology. Harvest is performed by routine methods.
In some chronic hematologic disorders, longer incubation or short term stimulation with PHA or other mitogen may be required. The appropriate procedure can be implemented only if clinical information is supplied with the specimen.
INTERPRETATION:
Twenty metaphase cells are analyzed under the microscope whenever possible. Two karyotypes are prepared from the mainline, and one karyotype from each sideline.
RESULTS:
Results are presented according to the International System for Human Cytogenetic Nomenclature (ISCN). Full explanation of the karyotype is provided and a short summary is written for each abnormal result.
