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Watchful waiting : Close monitoring without active treatment. This may be a reasonable choice for older men with small prostate tumors that might grow very slowly. If the situation changes, active treatment can be started.

White blood cells or White cells: Called leukocytes, these cells help defend against infection. Certain cancer treatments such as chemotherapy can reduce the number of these cells and make a person more vulnerable to infection - sometimes with deadly consequences.

W.H.O.: World Health Organization

Wire localization : A procedure used during a surgical breast biopsy when the lump is hard to find or when there is an area that looks suspicious on X-rays. A hollow needle is placed into the breast and x-rays are taken to guide the needle to the area in question. Once on location, a fine wire is inserted through the center of the needle and small hook at the end of the wire helps keeps the needle in place. The hollow needle is then removed, and the surgeon uses the wire path as a guide to find the abnormal area to be removed.