PR negative

Definition of progesterone receptor negative
National Cancer Institute

progesterone receptor negative

(proh-JES-teh-rone reh-SEP-ter NEH-guh-tiv)
Describes cells that do not have a protein that binds to the hormone progesterone. Cancer cells that are progesterone receptor negative do not need progesterone to grow. This means that they will keep growing when progesterone is not present and do not stop growing when treated with substances that block progesterone from binding. Also called PR negative.

Source: NCI Dictionary of Cancer Terms