Breast cancer tumors usually start in cells in the lobules (milk-producing glands) or ducts (the pathways that move milk from the lobules to the nipple). Invasive breast cancer means it has spread from the ducts or lobules to surrounding breast tissue. Metastatic means the cancer cells have spread to distant sites in the body, such as the bones or liver.

Breast cancer types

  • Invasive ductal carcinoma (IDC) is the most common.
  • Ductal carcinoma in situ (DCIS) is non-invasive ductal cancer.
  • Invasive lobular carcinoma (ILC) accounts for about one in 10 invasive breast cancers.
  • Lobular carcinoma in situ (LCIS) is the non-invasive form of ILC.
  • Less common types include: inflammatory breast cancer, Paget disease, Phyllodes tumor (develops in connective breast tissue), and angiosarcoma (a rare complication of breast radiation therapy or lymphedema).

Breast cancer facts

About 230,000 new cases are diagnosed each year, and nearly 3 million breast cancer survivors are alive in the U.S.  Still, breast cancer is the second leading cause of cancer death among women. Although it occurs mostly in women, men can get it, too.

Tyrer-Cuzick Risk Assessment Calculator

The Tyrer-Cuzick Risk Assessment Tool, a nationally accepted standard based on science, helps to measure women’s breast cancer risk factors based on family history, and helps women to better understand their breast cancer risk factors. It allows health professionals to estimate a woman’s risk of developing invasive breast cancer over the next five years and up to age 90.

Take the Tyrer-Cuzick Breast Cancer Risk Assessment.

*This tool can’t accurately estimate breast cancer risk for women:

  • Carrying a breast-cancer-producing mutation in BRCA1 or BRCA2
  • With a previous history of invasive or in-situ breast cancer
    • Lobular cancer in- situ (LCIS)
    • Ductal cancer in-situ (DCIS)
  • In certain other subgroups

Causes of breast cancer and risk factors

The lifetime risk for women has increased from 10 percent in the 1970s to a 12.4 percent (or a 1 in 8) chance today. The strongest risk factor is aging. 

Other risk factors include:

  • Inherited changes in certain genes, including BRCA1 and BRCA2.
  • Breast density. Denser breasts are at high risk.
  • Family history, especially if a relative was diagnosed younger than age 50.
  • Radiation therapy to the chest before age 30.
  • Age at menstruation. Have your first period before age 12 increases the risk.
  • Age at child bearing. Having your first child after age 35 or no childbearing boosts the risk.
  • Late menopause. Levels of estrogen remain high, increasing cancer risk, when women start menstruating early and enter menopause late.
  • Long-term use of hormonal therapy in menopause.
  • Use of the drug DES between 1941 and 1970 to prevent miscarriage.
  • Having two or more breast biopsies due to non-cancerous conditions.
  • Race. White women are diagnosed more often than other races, although African-American women now have about the same risks of getting diagnosed as white women but the risk of dying from the disease remains higher for African-Americans.

Controllable lifestyle factors can also increase the risk of breast cancer, such as being overweight or obese, sedentary, and drinking alcohol more than occasionally.

Other causes and risk factors, including unclear factors such as diet and exposure to environmental toxins, may also play a role.


There is no sure way to prevent breast cancer. Exercising four or more hours a week and keeping a normal weight can lower the risk. Having children while young and breastfeeding for long periods also reduces risk. For women at high risk, options include taking tamoxifen or other drugs to prevent breast cancer, and having surgery to remove breasts and/or ovaries.


Mammograms are the gold standard for detecting breast cancer early. Routine mammograms are recommended for women 40 and older unless they have risk factors that indicate starting sooner. UR Medicine Breast Imaging has several convenient locations and provides state-of-the- art digital mammography, dedicated breast ultrasound and interventional procedures to detect breast cancer.

Q&A: Breast Cancer Screening

Get answers to commonly asked questions about screening and diagnosis.