The Gray Line Between Breast Cancer and Abnormal Cells

The incidence of breast cancer is rising, and the drumbeat advocating early detection is growing louder. However, important facts about certain types of breast cancer are getting lost in all the noise.

Approximately one-quarter of all new breast cancer diagnoses are ductal carcinoma in situ (DCIS).

DCIS describes the presence of abnormal cells that have not spread beyond the milk ducts. On mammograms, DCIS appears as microcalcifications, or tiny specks of calcium. These are common and are usually associated with a benign condition. Radiologists look for microcalcification patterns, which alerts them that the surrounding tissue might be cancerous. Only a small tissue sample (biopsy) can confirm DCIS. Physicians generally treat DCIS as invasive breast cancer.

Before widespread mammography screening, DCIS diagnoses were rare. In his book, Should I Be Tested for Cancer?, author and physician H. Gilbert Welch, M.D. cites some interesting studies about DCIS.

In one study, physicians reviewed thousands of breast tissue biopsies from the 1950s and '60s in two distant cities. The women had DCIS, but radiologists missed it at the time, or it wasn't treated.

Seventy-five and 89 percent, respectively, of the women in each city did not develop invasive breast cancer over the following 20 years. Among women treated only with excisional biopsy, which removes the abnormal area and some of the surrounding normal tissue, 90 percent did not develop breast cancer after 10 years.

Welch cites another study that compared life expectancy of women treated for breast cancer to healthy women of similar age. Women with metastatic cancer were 12 times more likely to die, and women with early-stage invasive breast cancer were twice as likely to die. However, women with DCIS were 20 to 30 percent less likely to die.

Welch concludes that the majority of women with DCIS don't develop invasive breast cancer, and for those who do, the cancers grow slowly. Watching the DCIS closely, rather than treating it as invasive cancer, may make sense. Furthermore, according to the American Medical Association, after two decades of detecting and treating DCIS, there is no convincing evidence there's been a substantial reduction in invasive breast cancer incidence, which we'd expect if we were catching breast cancers earlier.

If you have DCIS, learn what type of cells you have; it can make a difference in your treatment. Get a second opinion. Your diagnosis may depend on the pathologist who looks at the biopsy sample. An incorrect diagnosis may result in the wrong treatment, or ineffective treatment. Ask your physician about monitoring the DCIS for changes, rather than treating it immediately.


Ductal Carcinoma in Situ (DCIS).

Esserman, Laura, Shieh, Yiwey, and Thompson, Ian. "Rethinking Screening for Breast Cancer and Prostate Cancer." JAMA 302(15) (2009): 1685-1691.

Welch, Gilbert H. Should You Be Tested for Cancer? Maybe Not and Here's Why. Berkeley and Los Angeles, California, University of California Press, 2004.