31.   Sonograms are performed in tandem with mammograms for women with particularly dense breast tissue, where early evidence of cancer is often missed.

32.   Surgeons can never be sure they have removed all the breast tissue, and any cells left behind retain their malignant potential.

33.   Tamoxifen works by blocking estrogen receptors in breast tissue.

34.   That could explain why the chemical would do most of its harm in breast tissue.

35.   That removes just the breast tissue, but not the skin and nipple, the way a total mastectomy does.

36.   The big advantage, researchers say, is that it seems not to stimulate breast tissue, as estrogen does.

37.   The cut rips open, revealing spongy yellow breast tissue.

38.   The first to reach the market, tamoxifen, blocks the ability of natural estrogens to stimulate growth of breast tissue.

39.   The devices rely on digital imaging, a technique experts say offers clearer, more detailed pictures of some breast tissue than traditional X-ray film.

40.   The often denser nature of breast tissue in younger women can make it harder to spot problems.