The grade of a tumor depends on: how abnormal the cancer cells look under a microscope, and how fast the cancer cells are growing. The pathology report may describe two different kinds of grade: nuclear grade and histologic grade. Nuclear grade describes the nucleus (headquarters of the cell that contains the DNA). Histologic grade describes what the rest of the cell looks like.
For more information, see Breastcancer.org's page on Cell Grade.
Audio contributed by: Larry King