watchful Waiting - Also known as active surveillance or observation, it is the least invasive treatment strategy that simply means that a physician and a patient are working together to actively observe the progression of the cancer or tumor.

wedge - A metal filter of triangular cross-section placed within a radiation beam to intentionally feather the radiation intensity from one side of the beam to the other.

white blood cells - Cells that circulate in the blood and are responsible for both directly and indirectly attacking foreign invaders of the body. -

wire localization - Guided by an imaging modality such as magnetic resonance imaging, a wire is inserted through a hollow needle to a lesion, or suspicious area of cells and tissue. The wire then guides the surgeon to the area so that the abnormal tissue can be surgically removed for examination. -