Glossary — T

A T-score is a number generated by a DEXA bone density scan that tells you how your bone density compares to the average peak bone density of a healthy young adult of the same sex. It is the primary measure used to diagnose osteoporosis and osteopenia in postmenopausal women and older men.

Tamoxifen is an oral medication that blocks estrogen from binding to cancer cells, slowing or stopping the growth of hormone-receptor-positive breast cancers. It has been used for decades both to treat breast cancer and, in high-risk individuals, to help reduce the chance that breast cancer will develop in the first place.

Thermography uses a specialized infrared camera to create a heat map of the body's surface, detecting differences in skin temperature that may reflect activity in underlying tissue. While it has been studied as a potential breast cancer screening tool, it is not currently recognized as a replacement for or equivalent to mammography.

A tissue expander is a temporary implant placed beneath the chest muscle after a mastectomy. Over the following weeks or months, saline is gradually injected into it through a small port to slowly stretch the skin and muscle, creating a pocket large enough to accommodate a permanent breast implant.

Trastuzumab (brand name Herceptin) is a monoclonal antibody — a laboratory-made protein — designed to attach to the HER2 receptor on cancer cells. By blocking this receptor, it slows the growth of HER2-positive breast cancers and helps the immune system identify and attack those cells.

Triple-negative breast cancer (TNBC) is defined by what it lacks: the estrogen receptor, the progesterone receptor, and the HER2 protein are all absent or low on the cancer cells. Because none of these targets are present, hormone-blocking drugs and HER2-targeted therapies do not work for TNBC — but chemotherapy and newer immunotherapy options remain effective.

A tumor is an abnormal growth of cells that forms a lump or mass. Tumors can be benign (non-cancerous), meaning they grow slowly and do not spread to other parts of the body, or malignant (cancerous), meaning they can invade nearby tissue and potentially spread elsewhere. The word itself simply means swelling.

A tumor marker is a substance — often a protein — that can be measured in blood, urine, or tissue and that is produced by cancer cells or by the body in response to cancer. Tumor markers are used to help diagnose certain cancers, monitor treatment response, and watch for recurrence, though they are rarely used as standalone diagnostic tests.