Case Studies: Test Result Definitions

The PathFinderTG® table of cumulative mutational information provides the way to integrate the molecular changes with the microscopic features of a sample(s). This table is used in the analysis of the test results.

Each column of the table represents a separate microdissection target that has been obtained from the submitted material(s). Each microdissection target (column) reflects unique cellular microscopic features such as whether it has been taken from normal appearing tissue, precancerous dysplasia or from different sites of cancer. At the top of each column, the microdissection target is briefly described. Each row of the table represents a distinct mutational marker being designated according to the cytogenetic location where it is found in the genome. By looking down each column, the reader can see which markers, if any, are mutated in that unique microdissection target. By scanning across each row, the reader can appreciate in which microdissection targets, if any, a particular marker is found to be mutated.

Mutations are documented in color while the absence of detectable mutation is shown by a box without coloration. In the variety of sample tables, the case table examples have blanks for all marker results that have no mutations or noninformative status. When there is an absence of detectable mutation it is referred to as a “NO LOH” (absence of allelic imbalance) or “NO MUT” (no DNA sequence point mutation) or a “NI” which is a noninformative status.

Mutations are shown in color together with a numerical percentage value. The numerical percentage is the calculated percentage of cells that are mutated for the particular marker in that specific microdissection targets. 100% would indicate that all cells in the specific target are mutated whereas 50% would signify that half the cells of the target are mutated.

Red and blue coloration are utilized to distinguish between the two different polymorphic alleles that are subject to loss of heterozygosity (allelic imbalance). By convention, red coloration indicates that the shorter of the two polymorphic microsatellite marker alleles is relatively deficient while blue indicates that the longer of the two polymorphic microsatellite marker alleles is relatively deficient. In this way it is possible to detect discordant (different) mutations of the same marker in separate locations within a cancer. Green coloration is reserved for DNA sequence point mutational damage and purple is used to indicate microsatellite instability. Microsatellite instability is not given a percentage designation as it is not possible to accurately define the proportion of affected cells.