A tumor that is at the original site where it first arose. For example, a primary breast tumor is one that arose in the breast as opposed to one that arose elsewhere and metastasized (spread) to the breast. The original tumor is sometimes called “the primary.” It is rare for cancers that originate elsewhere to spread to the breast. Most cancers IN the breast are breast “primaries”. Breast cancer can and does spread to other organs. As it turns out, if a breast cancer is going to spread elsewhere, it seems to have a propensity for spreading to lymph nodes, lung, bones, liver, or brain more than anywhere else.

A female hormone and the principal progestational hormone that is made mainly by the corpus luteum in the ovary and by the placenta. Progesterone prepares the lining (endometrium) of the uterus (the womb) to receive and sustain the fertilized egg and so permits pregnancy. Similarly refers to synthetic versions of the hormone. Also known as progestational hormone. In the breast, cancer cells can have cell receptors that interact with progesterone in the blood stream. (Progesterone receptor [PR] positive). This has less significance than being “estrogen receptor +”.

An artificial substitute or replacement of a part of the body such as a tooth, eye, a facial bone, the palate, a hip, a knee or another joint, the leg, an arm, etc. A prosthesis is designed for functional or cosmetic reasons or both. In breast cancer disease, the term prosthesis usually refers to a padding worn inside the bra to restore the shapeliness of the breast after mastectomy, if a reconstruction has not been done.