TEST ACRONYM

FULL TERMINOLOGY

synthesis phase

DEFINITION

S-phase fraction test: a test that shows how fast a cancer is growing

WHEN TEST WOULD BE PERFORMED

To determine a tumor's histologic grade, pathologists examine the breast cancer cells and their patterns under a microscope. A sample of breast cells may be taken from a breast biopsy, lumpectomy or mastectomy.

INFORMATION VALUE

S-phase is the time when the cells copy their DNA so that the new cells each have a full set of genes. They 'synthesise' DNA just before the begin to divide. So the proportion of cells in s-phase in your pathology sample gives your doctor an idea of how active the cancer is. The more cells that are in s-phase, the more are dividing, so the faster the cancer will grow.

CAUTION

Even in very experienced labs, these tests are hard to do reliably. That's why many doctors depend on other information to make the best treatment decisions.