Ploidy Analysis

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Ploidy analysis

Definition

Ploidy analysis is a test that measures the amount of DNA in tumor cells. It is also called DNA ploidy analysis.

Purpose

DNA ploidy analysis is used in addition to the traditional grading system as another way to evaluate how malignant a tumor might be. The advantage of this test is that it provides a numeric, and therefore objective, evaluation of how aggressive the cancer might be. Because this test was relatively new in 2001, and the significance of information gained by this test was not completely understood, this test had not yet replaced traditional systems of tumor grading . It would be used only to supplement those tests in order to give the doctor as much information about the nature of the tumor as possible. Doctors may also use this test to help predict how a tumor may respond to the planned therapy.

Precautions

This test requires a certain sample size in order to be performed; the specimens acquired in some biopsies may not provide enough material to run the test. It is also important in this test that only tumor material is used to create the population of cells which are analyzed, as any healthy tissue included can significantly affect the results. Interpretation of the numeric results of this test is still somewhat controversial. There is no commonly accepted system for interpreting the results; in addition, the results of the test can vary greatly from one part of a tumor to another.

The way the test should be used for optimum results in the management of cancer patients remained questionable due to many unexplored issues, and results due to the lack of data accumulated so early into its history. Although research has shown that in general, patients whose tumors have lots of cells with abnormal amounts of DNA have shorter survival times, the results of the test have not, for the most part, been that successful in predicting how an individual patient will do.

Description

Ploidy analysis is performed on a sample of the tumor to determine how many of the cells have the normal amount of DNA and how many have more or less than the normal amount (called aneuploid). Cancerous cells are rapidly dividing cells. When cells divide there is a period before the actual division during which the cells have twice the normal amount of DNA. Tumors with higher proportions of aneuploid cells are generally considered to be more aggressive tumors.

Taking a sample of a tumor is called a biopsy . How and where that is done depends on where the tumor is located. Tissue from the surface of body cavities like the mouth or the vagina can be easily sampled from a simple scraping, in a doctor's office. For some types of tumors (such as in breast cancer ) it is possible to extract enough cells with a needle and syringe. Often, however, a surgical biopsy will need to be performed in the hospital. The tissue removed will be taken to a laboratory and analyzed.

Preparation

Patient preparation for the collection of a tumor sample through biopsy will vary depending on the site of the tumor. Most biopsies call for little that the patient will need to do. For biopsies of internal organs the patient may need to avoid eating after midnight before the test, in case a complication occurs and surgery may be necessary. Patients should try not be fearful of the collection of the sample. Doctors will make the procedure as painless as possible by using appropriate anesthetic.

Aftercare

There can be a little soreness at the biopsy site for a few days following the procedure; acetominophen or another over-the-counter painkiller can be used if the patient feels a need for pain relief. If the site becomes swollen, red, or hot to the touch it may be infected and the patient should contact their physician.

Risks

The risks involved in this test are only the risks inherent in having a biopsy. Since this procedure uses tissue obtained through a biopsy already being performed for the purpose of grading the tumor, there are no additional risks to the patients involved as a result of the test. This test can also be performed on stored biopsy tissues that were obtained at some previous time.

Normal results

Normal cells, most of the time, have two sets of 23 chromosomes, one from each parent, for a total of 46 chromosomes. Normal cells contain four sets-or 92 total chromosomes- for a very brief time right before they divide. Normal tissues have a largely homogenous population of cells containing 46 chromosomes, with a very small percentage of dividing cells that contain 92.

Abnormal results

Tumors have lots of cells that are in the process of reproducing, so tumor tissues typically have a significant population of cells, containing 4 sets of chromosomes, that are about to divide, in addition to the large population of normal cells containing 2 sets of chromosomes. Tumor cells can also contain numerous other variations of normal. Any tissue comprised of significant numbers of cells that have anything but two sets of chromosomes would be considered abnormal.

See Also DNA flow cytometry