Ploidy (Number of Chromosomes)

Ploidy is a measure of the number of chromosomes in a cell. Chromosomes are the threadlike structures that contain the genetic material known as DNA. As cells grow and divide to make new cells, chromosomes play a key role in making sure that DNA is copied and distributed correctly.

As part of your diagnosis, a pathologist may look at whether the cancer cells contain the normal amount of DNA. To do this, the pathologist looks at the number of chromosomes in the cancer cells and reports them as:

• Diploid: This means that a proportion of cancer cells have the same number of chromosomes as normal, healthy cells (two sets of 23 each). They tend to be slower-growing, less aggressive cancers.
• Aneuploid: This means that a proportion of cancer cells have too many or too few chromosomes. When cancer cells are rapidly dividing, mistakes in the distribution of chromosomes can happen, resulting in some cells having too many chromosomes and others too few. An aneuploid cancer may be more aggressive than a diploid cancer.

Although ploidy may provide you and your doctor with useful information, the test is considered optional and is not done routinely. Therefore, it’s possible that ploidy won’t be included in your pathology report. Experts don’t yet agree on how to use the results in the process of making treatment decisions.