Rate and Grade of Cell Growth

Under the microscope, your pathologist looks for clues that will help give a picture of the cancer's growth patterns, including:

• Rate of cancer cell growth: The proportion of cancer cells growing and making new cells varies from tumor to tumor—and may help to predict how aggressive a cancer is. If more than 6% to 10% of the cells are making new cells, the rate of growth is considered unfavorably high. Your doctor may order special tests, called S-phase fraction and Ki-67 tests, to measure rates of cell growth. Tests of growth rate are sometimes unreliable. Your doctor may look at the results of these tests, but base most treatment decisions on other, more reliable cancer characteristics.

• "Grade" of cancer cell growth: Patterns of cell growth are rated on a scale from 1 to 3 (also referred to as low, medium, and high instead of 1, 2 or 3). Calm, well-organized growth with few cells reproducing is considered grade 1. Disorganized, irregular growth patterns in which many cells are in the process of making new cells is called grade 3. The lower the grade, the more favorable the expected outcome. At the same time, the higher the grade, the more vulnerable the cancer is to treatments such as chemotherapy and radiation. Therefore, women with a "high" or "grade 3" breast cancer can also feel hopeful about treatment.

• Dead cells within the tumor: It's tempting to think that the only good cancer cell is a dead cancer cell. However, necrosis (or dead tumor cells) is one of several signs of excessive tumor growth. It means that a tumor is growing so fast that some tumor cells wither and die because there's not enough blood supply to feed all of them. This is a small feature of the cancer but an unfavorable one, because the growth is at such a high rate.