Sorted By Test Name - Mayo Medical Laboratories

LN
8911
SCE
926
Chromosome Analysis, Lymphoid Tissue
Clinical Information: Chromosomal abnormalities play a central role in the pathogenesis, diagnosis,
and monitoring of treatment of many hematologic disorders. The observation of a chromosomally
abnormal clone is consistent with a clonal neoplastic process. Certain chromosome abnormalities can help
classify the type of lymphoma. For example, t(14;18)(q32;q21.3) involving the IGH and BCL2 genes is
usually indicative of a follicular lymphoma. A translocation between C-MYC and IGH genes or a
t(8;14)(q24.1;q32) are both associated with Burkitt's lymphoma. Cytogenetic studies often can help
distinguish between B-cell and T-cell disorders. Structural abnormalities involving breakpoints at any
immunoglobulin locus is consistent with a B-cell disorder; structural abnormalities involving breakpoints
at a T-cell receptor site are usually associated with a T-cell disorder.
Useful For: Assisting in the classification of certain cases of lymphoma
Interpretation: The observation of a chromosomally abnormal clone is evidence of a clonal neoplastic
process. Certain chromosome abnormalities also may be associated with certain morphologic
classifications. However, a normal karyotype does not eliminate the possibility of a neoplastic process. On
rare occasions, the presence of an abnormality may be associated with a congenital abnormality that is not
related to a malignant neoplastic process. Follow-up with a medical genetics consultation is
recommended.
Reference Values:
46,XX or 46,XY. No apparent chromosome abnormality.
An interpretive report will be provided.
Clinical References: 1. Pierre RV, Dewald GW, Banks PM: Cytogenetic studies in malignant
lymphoma: possible role in staging studies. Cancer Genet Cytogenet 1980;1:257-261 2. Dewald GW,
Jenkins RB: Cytogenetic and molecular genetic studies of patients with monoclonal gammopathies. In
Neoplastic Diseases of Blood. Second edition. Edited by PH Wiernik, GP Canello, RA Kyle, CA Schiffer.
New York, Churchill Livingstone, 1991, pp 427-438
Chromosome Analysis, Sister Chromatid Exchange (SCE) for
Bloom Syndrome, Blood
Clinical Information: Bloom syndrome is a genetic disorder associated with various congenital
defects and predisposition to acute leukemia, pulmonary fibrosis, and Hodgkin lymphomas. Carcinoma
also is commonly seen in these patients. Approximately one fourth to one half of patients develop some
type of cancer with a mean age of 25 years at onset. The severity and age of onset of cancer varies among
patients. These patients often have prenatal or postnatal growth retardation, short stature, malar
hypoplasia, telangiectatic erythema of the face and other regions, hypo- and hyperpigmentation, immune
deficiencies, occasional mild mental retardation, infertility, and high-pitched voices. Bloom syndrome is
an autosomal recessive disorder caused by mutations in the BLM gene located at 15q26.1. While multiple
mutations have been detected, the use of molecular testing to diagnose Bloom syndrome is limited in
many ethnic groups. Patients with Bloom syndrome demonstrate a high frequency of chromosome
abnormalities when their cells are cultured. Thus, cytogenetic studies can be helpful to establish a
diagnosis. Bloom syndrome results in 2 characteristic cytogenetic abnormalities. First, the cells are at
increased risk for random breaks leading to fragments or exchanges between nonhomologous
chromosomes. Second, cells in these patients have an increased frequency of sister chromatid exchanges
(SCE: exchange of material between homologous chromosomes) of approximately 10-fold to 20-fold
higher than average. This test is diagnostic for Bloom syndrome. Carrier testing for Bloom syndrome is
performed by different methodologies, so this test should not be ordered for that purpose.
Useful For: As a diagnostic test for Bloom syndrome
Interpretation: The observation of a 10-fold or more increase in spontaneous sister chromatid
exchange (SCE) relative to a control specimen and historical reference values is a diagnostic cytogenetic
finding for Bloom syndrome. Spontaneous SCE that is more than 10 times greater than the normal control
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