Fluorescence In Situ Hybridization

FISH is a very useful technique for detection of targeted BCL-associated chromosomal abnormalities and can detect both structural and numerical chromosomal abnormalities. FISH overcomes one of the problems with routine cytogenetics on BCL samples, that is, the need for metaphase cells, as it can be done with either metaphase or interphase preparations. Genomic probes for the breakpoints of many different BCL translocations and for gene deletions are now readily available. FISH assays are particularly useful in detection of chromosomal translocations in which the breakpoints are widely dispersed, because FISH probes are much larger than probes and primers used in SBA and PCR. For example, FISH probes can detect almost all of the MYC 8q24 breakpoints in the t(8;14)(q24;q32) translocations associated with BL. FISH detects some genetic abnormalities that are karyotypically silent.

Figure 32-5. Capillary electrophoresis (CE) printouts of two IGH PCR analyses for B-cell clonality. (a) A polyclonal B-cell population produces multiple small peaks on the CE printout; to be considered monoclonal, a peak should be at least double the height of the peaks from the background polyclonal B cells. (b) A monoclonal B-cell population produces one sharp peak on CE (or two in some cases). The interpretation of the CE printouts is probably more objective than interpretation of routine agarose or polyacrylamide gels. (Black peaks are size marker standards.)

Figure 32-5. Capillary electrophoresis (CE) printouts of two IGH PCR analyses for B-cell clonality. (a) A polyclonal B-cell population produces multiple small peaks on the CE printout; to be considered monoclonal, a peak should be at least double the height of the peaks from the background polyclonal B cells. (b) A monoclonal B-cell population produces one sharp peak on CE (or two in some cases). The interpretation of the CE printouts is probably more objective than interpretation of routine agarose or polyacrylamide gels. (Black peaks are size marker standards.)

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