Testing: Tissue Testing

Lymph system tissue can now be examined by two different cutting-edge techniques.

The first, flow cytometry, can identify the cells involved by testing for the presence or absence of compounds on the membrane of the cells. These markers are called clusters of differentiation (CD) and are listed numerically. By developing a list of the CDs present on the cells, it is possible to classify the cells.

The second method is to examine the genes of the cells by testing for specific DNA pieces. One can then say, for example, that a person has NHL of mature B cells with CD5, CD20, and CD22 and that these cells have an abnormal chromosome translocation between chromosomes 8 and 14.

Such genetic testing has been advanced in recent years with the use of the "Lymphochip" by the Staudt Lab at the US National Institutes of Health. A small tissue sample can be tested against an array of 18,000 genes on a single glass chip.

These recent advances are helping target treatments to specific types of lymphoma. One in diffuse large b-cell lymphomas show there are two distinct subtypes based on cell behavior - doctors can target their treatment based on how the cells react during testing.