Most of this growing incidence is occurring among women over age 50. More cases are being found partly because more women are getting mammograms, or breast X-rays, that detect the disease. But the actual number of breast cancers also appears to be rising. This year, 46,000 American women will die of the disease.

BENIGN BREAST DISEASE: Women who have had benign breast lumps suspicious enough to be biopsied have twice the ordinary risk of getting breast cancer.

CAPTION: A GROWING THREAT (data from this graphic was not available.) CAPTION: BREAST CANCER IN THE WASHINGTON AREA Across the Washington area, women are dying of breast cancer at a higher rate than the nation as a whole. DEATHS PER 100,000 WOMEN, 1985-1989 Anne Arundel Co. ....... 30.58 Baltimore............... 30.95 Howard Co. ............. 29.36 NATIONAL MORTALITY RATE: 27.4 Montgomery Co. ......... 28.76 Prince George's Co. .... 30.26 District................ 33.00 Alexandria.............. 28.30 Arlington Co. .......... 28.30 Fairfax Co. ............ 30.30 Loundoun Co. ........... 38.70 Prince William Co. ..... 33.60 SOURCES: National Cancer Institute; Virginia Center for Health Statistics; D.C. Public Health Commission; Bureau of Cancer Control Compiled by Amy Goldstein.