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Tumor karyotype showing the t(11;22) typically associated with Ewing’s sarcoma/PNET |
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Blood & Tissue Cytogenetics
Blood Cytogenetics: Chromosomal analysis on peripheral blood is a good way to look at the constitutional chromosomal make-up or karyotype of an individual. Peripheral blood is drawn and cultured in tissue culture media supplemented with a mitogen, PHA (phytohemagglutinin), that causes the lymphocytes to grow in culture. After 48 to 96 hours in culture, metaphase chromosomes are “harvested” and slides made for chromosome analysis. Peripheral blood can be used as a substitute for a bone marrow aspirate when one cannot be obtained and circulating blasts are present.
Bone Marrow Cytogenetics: Bone marrow cytogenetic analysis is performed on patients with leukemia, lymphoma or other hematological disorders. These patients often have acquired clonal chromosomal abnormalities that can be diagnostic and/or prognostic.
Breakage Studies: Ataxia telangiectasia (AT) is a rare, autosomal recessive chromosomal breakage syndrome characterized by progressive cerebellar ataxia, telangiectasias, immune deficiency and a predisposition to malignancy. Fanconi anemia (FA) is a rare, autosomal recessive condition characterized by growth retardation, thumb abnormalities/radial aplasia, pigmentary anomalies and hematological disorders, including eventually MDS and AML. Both disorders are associated with a DNA repair defect that leads to an increased rate of spontaneous chromosomal breakage when blood is exposed to mitomycin C and/or diepoxybutane.
Solid Tumor Cytogenetics: Cytogenetic analysis can be an important adjunct to solid tumor diagnosis and management. This is particularly true in the case of the small round blue cell tumors of childhood (Ewing’s sarcoma/PNET; rhadomyosarcomas).
Tissue Cytogenetics: Solid tissue specimens can be cultured as a source for mitotic cells for chromosomal analysis. Products of conception (POC) specimens from the first trimester spontaneous abortions are often studied. Around half of these are chromosomally abnormal, typically aneuploidies. Tissues from intrauterine fetal demises or stillborns can also be studied and may help confirm abnormal prenatal results. Tissues should be of fetal, not maternal, origin (e.g. fetal tissue, membranes, villi). Internal organs/diaphragm obtained at autopsy can be used. Skin punch biopsies may also be obtained to rule out chromosomal mosaicism or to culture for biochemical and/or molecular analysis.
