By Edward C. Geehr, M.D.,
An early cancer diagnosis often means an improved outcome. But not always. Every year, approximately 50,000 women are diagnosed with ductal carcinoma in situ (DCIS) of the breast. Often called non-invasive or Stage 0 breast cancer, DCIS responds well to treatment. Unfortunately, approximately 20% of cases may be misdiagnosed.
In DCIS, abnormal cells are contained in the lining of the milk ducts. In situ, which means “in place,” the cancer cells haven’t left the ducts to invade nearby breast tissue. Although DCIS is considered to be non-invasive, if left untreated, about 20%-30% of women will progress to invasive cancer.
Experts believe misdiagnosis happens because doctors disagree over which criteria they use. For example, some pathologists hold that lesions less than 2 millimeters preclude the diagnosis regardless of cell appearance, while others rely on the presence of characteristic changes regardless of lesion size.
But even appearance can lead to disagreement. One expert reviewed approximately 600 breast cases and found discrepancies in 141 of them, including 27 cases where DCIS was misdiagnosed. DCIS is typically diagnosed from microscopic core needle biopsies. It can be difficult to distinguish between low-grade DCIS and benign conditions, such as atypical ductal hyperplasia which can be misread as much as 20% of the time.
Another factor may be that many breast biopsies each year are performed in community hospitals where pathologists have limited exposure to DCIS or unusual breast cancer tumors. This has led the College of American Pathologists to call for a voluntary certification program for pathologists who read breast tissue. They’ve proposed a minimum requirement of 250 breast cases a year to be certified.
The potential for misdiagnosis and overtreatment of DCIS was recently disputed in a discussion about the age to begin mammography. Before the widespread use of mammography in the 1980s, DCIS was rarely diagnosed. Until that time, most biopsies were performed after feeling lumps in the breast. By then, most lesions were usually well established as cancer, benign tumor, or cyst.
As noted, in a percentage of cases untreated, DCIS will progress to invasive cancer. And even though DCIS is 90% curable, many experts are concerned that patients and their doctors may decide on more aggressive therapy than is necessary, such as a combination of mastectomy, radiation, and drug therapy. In fact, the rate of double mastectomy for DCIS rose to 5% in 2005 from 2% in 1998.
So the benefits of earlier diagnosis are offset by potential misdiagnosis and over-treatment.