Investigators report headway against breast cancer, the disease that worries some women more than any other. The suspects they've identified -- from heredity to lifestyle -- may point you toward precautions.

Breast cancer is the most common cancer among women, except for non-melanoma skin cancers. After lung cancer, it is the second-leading cause of cancer death in women, according to the American Cancer Society (ACS).

Anatomy of an enigma

To understand the puzzle of breast cancer, you must understand how the breasts work.

The breasts consist of glandular tissue surrounded by fat. The glandular material secretes milk after a woman gives birth.

During the monthly menstrual cycle, the body begins the complex process of preparing the breast to make milk. The ovaries release hormones called estrogens that stimulate breast cells. The days before menstruation you may experience swollen, painful breasts that return to normal once the menstrual period begins, or that continue to grow if a woman is pregnant and will soon nourish a baby.

Month in, month out, breast cells change in response to hormonal stimulation throughout the reproductive years.

Longer menstrual life

Experts believe this constant stimulation presents problems. We do know that the breast is estrogen-sensitive, and we also know that certain estrogens appear to be carcinogenic. We also know that the greater the total number of ovulations a woman has in her lifetime, the greater the risk of breast cancer.

That means women who start menstruating early, before age 12, and have a late menopause, after age 55, run a higher risk. So do women who have had no children, or who had their first child after age 30.

With estrogen and other hormones as catalysts, breast cells continually receive the signal to change.

That puts the breast in a class with such other highly active anatomy as the intestinal tract, where cancer also is common. It seems "active" cells have more chances to change, compared with inactive fat cells such as those in the buttocks.

But what turns rapidly changing cells into cancer? Two women may share a seemingly identical profile, but one will get the disease and the other will not.

To solve that puzzle, researchers must continue to follow the clues.

The usual suspects

Cited here are some usual suspects in the breast cancer probe:

• Diet and lifestyle. Overweight women seem more prone to breast cancer. Fat cells can make and store estrogen, perhaps increasing this hormone's effect on the breast. Saturated fats, such as those in red meat and full-fat dairy products, have been closely linked to other types of cancer, and researchers are probing their role in breast cancer. Alcohol consumption can raise estrogen and increase risk. So can a sedentary lifestyle.

• Family history and genetics. A woman's risk increases if close blood relatives of either parent have had breast cancer. Scientists have discovered mutations in two genes, BRCA1 and BRCA2, which they blame for about 5 to 10 percent of breast cancer in the general population, but have higher rates in women of Ashkenazi Jewish ancestry. Around eighty percent of women who carry these genes will likely develop the disease. But experts believe just a fraction of the female population has one of these two genes.

• Personal history. "Lumpy" breasts, common among women, do not increase breast cancer risk. Several breast conditions are harmless, including fluid-filled sacs called cysts and solid round tumors called fibroadenomas. But cysts in two breast conditions, atypical ductal hyperplasia or atypical lobular hyperplasia, do increase cancer risk. Any unusual breast lump must be checked by a doctor; 80 percent prove to be benign. Previous cancer in one breast also is a risk factor.

• Our world. On the environmental front, research is under way into the role of pesticides, engine exhausts, and contaminants in food and water. Scientists have not confirmed any absolute link.

Reducing your risk

Over their lifetime, one in eight women will get breast cancer. Here's how you can decrease your risk:

• Get regular mammograms and breast exams. Talk with your doctor to see how often you should be tested and how young you should start. These are decisions that may be influenced by your risk factors. Mammograms can detect a lump far earlier than you can feel it.

• Think low-fat and high-fiber. Include five or more fruits and vegetables per day. A healthy, nutritious diet may help decrease the risk for several cancers.

• Try to keep your weight normal. A recommended range is a body mass index (BMI) of 19.5 to 24.9. To calculate your BMI, figure your weight in kilograms and divide it by your height in meters squared (kg/m²).

• Regular exercise will keep your weight down, and for younger women of normal or low weight, four or more hours a week may decrease hormone levels and help lower breast cancer risk..

• If you drink alcohol, stop at one drink a day (or less).

• Considering hormone therapy (HT) after menopause? Although HT may offer benefits for menopausal symptoms and in the prevention of osteoporosis, it increases other health risks. Talk to your health care provider to see what is best for you.

Preventive options?

• Tamoxifen. This anti-estrogen drug has long been used to treat breast cancer, but studies have found preventive benefits, as well. Tamoxifen (Nolvadex) cut breast cancer 42 percent in high-risk participants. Still, the National Cancer Institute reports the drug can have serious side effects, including a higher risk of endometrial cancer and blood clots. As a result, experts recommend limiting it to those at greatest risk.

• Raloxifene. This "designer estrogen" (brand name Evista) can cut the risk for breast cancer as well as tamoxifen can while imitating estrogen's benefits for your bones and heart. Like tamoxifen, it may increase the risk for blood clots.

• Aromatase inhibitors. This class of drugs decreases the body's estrogen by blocking the conversion of naturally produced androgen into estrogen. After menopause, most of woman's estrogen is made in tissues outside the ovaries from androgen. Currently, three drugs are approved by the FDA: anastrazole (Arimidex), exemestane (Aromasin), and letrozole (Femara). Possible side effects are decreased bone density and joint pain and stiffness.

• Prophylactic mastectomy. For women with a family history of breast cancer, removal of both breasts may reduce the risk. This option should be considered only after trying other preventive treatments and counseling.