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Prometaphase chromosomal study at 650 ~ 700 band level. a. metaphase spread; b. Karyotype of the same metaphase: 46, XX 3. Fragile X Study package: These studies are indicated in patients and families in whom X-linked mental retardation is suspected. In general, the package includes prometaphase chromosomal studies and DNA based molecular diagnosis for fragile X syndrome (please see detailed information in molecular tests for fragile X syndrome). 4. Chromosomal Breakage Studies - These studies are indicated as part of the diagnostic work-up for Fanconi's Pancytopenia, Ataxia-telangiectosia syndrome, and Bloom syndrome. Bone Marrow or leukemic blood Chromosome analysis is essential in the initial diagnosis, the prognosis of the hematological malignancy, including acute and chronic leukemia and lymphomas. It also plays an important role in the monitoring of the disease development, and the patient's response to treatment. Our chromosome study allows the identification of rearrangements observed in many types of these hematological disorders. An example of a common chromosomal abnormality found in leukemia is the presence of the Philadelphia chromosome (Ph). The presence of the Ph chromosome is diagnostic of chronic myelogenous leukemia. In addition to the Ph, as the course of the disease progresses, other chromosomal abnormalities may appear as well. With successful treatment, these abnormalities, except for the Ph chromosome, may disappear. Prenatal Cytogenetic Studies 1. Amniotic Fluid -These studies are performed on patients with a history of chromosomal rearrangements, advanced maternal age, increased or decreased alpha-fetoprotein levels, and abnormalities seen on ultrasound. Amniotic fluid can be obtained at approximately 12 to 17 weeks gestation, and the results of the karyotype are reported within 7 to 10 days, depending on the rate of growth of the cells in tissue culture. 2. Chorionic Villus Sampling (CVS) - These studies are also performed for the above mentioned indications for study as amniotic fluid. However, CVS can be performed at 9 to 12 weeks gestation, and the results are reported within 6 to 8 days, also depending on the rate of growth of the cultured cells. Currently, our lab is the only one in the state of Louisiana performing chromosome analysis on CVS. 3. Percuntaneous umbilical blood sampling (PUBS) - Fetal blood sampling obtained from the umbilical cord may be indicated when mosaicism is detected in amniotic fluid studies, when there is a high risk of chromosomal abnormality and gestational age is advanced, for third trimester diagnosis when delivery is imminent, and for diagnosis of Fragile X or chromosomal instability syndromes. Solid Tissue 1. Products of Conception - As many as 50% of spontaneous miscarriages are associated with chromosomal abnormalities. Successful karyotyping of the tissue may reveal critical information concerning the recurrence risk in future pregnancies. A late second trimester or a third trimester miscarriage of a nonviable fetus combined with clinical and pathological findings also raises the possibilities of chromosomal rearrangements. 2. Skin Fibroblasts - These can be submitted when peripheral blood is not available such as in the event that a patient has expired or in rare situations when mosaicism is suspected and the ratio of cells with chromosomal abnormalities of different tissues is evaluated. 3. Solid Tumors - Chromosomal abnormalities found in solid tumor are increasing daily. Many of them are associated with a specific type of solid tumor, and therefore, are of great importance in early diagnosis, prognosis and in the monitoring of the disease development. The type of tissue for the study is determined by the nature of the tumor. MOLECULAR CYTOGENETIC STUDIES (Fluorescence In Situ Hybridization, FISH)Standard cytogenetic analysis permits diagnosis of numerical and structural chromosome analysis, but it has limitations. Deletions smaller than several million base pairs are not routinely detectable. Chromosomal abnormalities with indistinct or novel banding patterns can be difficult or impossible to interpret. Analyzable metaphases may not be always possible to obtain (e.g. some types of solid tumors, autopsy material that has already been fixed). Chromosomal abnormalities which were previously difficult or impossible to detect with standard cytogenetic methods are now easily ascertained with FISH. This technique efficiently enables cytogeneticists to identify various numerical and structural alterations including aneuploidy, inversions, marker chromosomes, complicated or subtle translocations, and submicroscopic deletions and duplications. Our laboratory is equipped with the most updated knowledge and the best image system required providing this state-of-art service. Currently, we are implementing Multicolor FISH (M-FISH) and Comparative Genomic Hybridization (CGH) systems, which will greatly benefit cancer genetics studies and some difficult genetic cases. Clinical application of FISH 1.
Chromosome microdeletion syndromes: Microdeletion Syndromes and Percentage of Cases Resolved with FISH
2. Chromosomal structural abnormalities: Translocations, inversions, and duplications. Large translocation can be diagnosed by routine cytogenetics. However, complicated translocations and cryptic translocations often need the help of FISH analyses. 3. Oncogene amplifications or losses of antioncogene or gene rearrangement. For example: N-myc amplification in neuroblastoma and loss of P53 in B-cell CL. 4. Characterization of marker chromosome: Marker chromosomes are extra chromosomes of unknown origin. FISH, by far is the most effective and accurate method to identify the origin of markers. 5. Prenatal aneuploidy screen: Screen for chromosomes 13, 18, 21, X and Y.  FISH with probe TUPLE1 within DGS/VCFS chromosome region in a patient with VCFS. Solid arrow shows the deletion  Interphase FISH with bcr/abl probe on a bone marrow specimen from a patient suspected of CML. A positive fusion signal [t(9;22)] was present in each of the cells shown above Cytogenetic Diagnostic Lab Test ListPlease contact the department for sample specifications before shipping. To view the lab form and all tests, please open the Lab Test Form. |
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