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Breast Cancer: Causes, Diagnosis and Treatment

  • A disease in which cells in the breast grow erratically and turn into cancer
  • Types include ductal carcinoma in situ, infiltrating ductal carcinoma
  • Treatment includes surgery, chemotherapy, radiation
  • Involves breast center, general surgery


In a woman’s breast, there are 12 to 20 sections of tissue, called lobes, which surround the nipple like petals on a flower. Each lobe contains several glands, where milk is produced. The glands are connected by ducts that transport the milk to the nipple. Breast cancer typically starts in one of these structures, after a change in the DNA causes abnormal cells to grow.

Current statistics suggest that breast cancer will affect 1 in every 8 women in the United States, and, though it’s rare, the disease also affects some men. Fortunately, methods for detecting and treating breast cancer are continually improving. Today, patients may be offered a range of treatment options to suit their goals and needs.

“Breast cancer is the most well-researched cancer,” says Yale Medicine breast surgeon Danielle Bertoni, MD. She wants women to know that breast cancer has a very good prognosis. “Survival rates are very, very good for breast cancer,” she says. “Most breast cancer is curable and treatable. Even women with stage IV breast cancer can often live for many years.”

Who's at risk for breast cancer?

There are certain breast cancer risk factors that women can’t do anything about. For example, breast cancer is more likely to occur in women whose period started before age 12 or who experienced menopause after age 55.

In about 10 percent of patients, a high risk for breast cancer is inherited. Those with a family history of breast cancer may choose to be tested for mutations in the BRCA genes to determine whether they’re at high risk.

Other risk factors include a lack of exercise, alcohol consumption, use of hormone-based contraceptives and previous exposure to radiation therapy for cancer treatment. Women who give birth before age 30 or breastfeed their babies may have a reduced risk for breast cancer, which doctors believe is because they have fewer periods over the course of their lives.

“A lot of breast cancer is fed by estrogen,” explains Dr. Bertoni. “When you're pregnant or are breastfeeding, you have a much lower state of estrogen, and the same thing is true when you're post-menopausal.” However, getting your period young and entering menopause late both prolong estrogen exposure, she says, which is a risk factor for breast cancer.

Though 99 percent of cases occur in women, over 2,000 cases of breast cancer are diagnosed in men in the U.S. each year. For both women and men, the risk increases with age.

What are the types of breast cancer?

screeningIt can be helpful to think of breast cancer as either invasive (actively spreading to surrounding tissue) or noninvasive (not actively spreading).

Ductal carcinoma in situ (sometimes called DCIS), which accounts for between 20 percent and 30 percent of all breast cancers, is a noninvasive breast cancer that develops inside the breast milk ducts. Infiltrating ductal carcinoma, which accounts for up to 80 percent of all breast cancers, is an invasive type that also develops in the ducts, but then spreads to the lobe tissue.

There are other, less common invasive types (e.g., infiltrating lobular carcinoma, medullary carcinoma, mucinous carcinoma and tubular ductal carcinoma). Two other rare types of breast cancer, inflammatory carcinoma and Paget’s disease, are defined by their unique skin symptoms, which can include thickening, pitting and flakiness.

How is breast cancer diagnosed?

In some cases, patients will see a doctor after they’ve noticed a lump in the breast or have other symptoms like breast pain, nipple discharge or skin changes. A breast tumor also may be detected during a physical exam or on a screening mammogram (an X-ray of the breast).

Talk to your health care provider about when you should begin having screening mammograms. Women who are at average risk for breast cancer should consider starting yearly screening mammography at age 40. 

If a tumor is detected, additional testing may be needed such as a diagnostic mammogram and/or breast ultrasound. Breast cancer is then typically diagnosed through a core needle biopsy. Though it is unusual, a surgical biopsy can be performed if a core needle biopsy is not possible. 

How is breast cancer treated?

If cancer is confirmed, the doctor and patient work together to determine an appropriate treatment plan.

Most breast cancer patients undergo some form of surgery. The surgeon may recommend mastectomy (complete removal of the breast) or a lumpectomy (also called breast conservation treatment), which allows the patient to keep most of the breast. Mastectomy is better for certain types of cancer or larger tumors, but both procedures can be effective for early-stage cancers. After the tumor has been removed, the option to rebuild the breast (reconstruction surgery) is available.

Other treatments may include chemotherapy drugs and/or radiation therapy to keep the cancer from spreading further. In addition, the doctor might suggest biological or hormonal therapies, which are customized to fit each patient’s needs.

What is Yale Medicine's approach to treating breast cancer?

At Yale Medicine, we provide the highest standard of care, following all national guidelines and standards. We have highly trained physicians and staff. “At the same time,” says Dr. Bertoni, “we try to provide an individualized treatment plan and approach for patients, taking into account their background and desires.”