Q. What is D.C.I.S.?
A. D.C.I.S. stands for ductal carcinoma in situ. It is a small pileup of abnormal cells in the lining of the milk duct. You cannot feel it because there is nothing to be felt; there is no lump. But the cells can be seen in a mammogram, and when a pathologist examines them, they can look like cancer cells. The cells have not broken free of the milk duct or invaded the breast. And they may never break free. The lesion might go away on its own or it might invade the breast or spread throughout the body. That raises questions about what, if anything, to do about it.
Q. Is D.C.I.S. cancer?
A. It is often called Stage 0 cancer, but researchers say their view of cancer is changing. They used to think cancers began as clusters of abnormal cells, and unless they were destroyed the cells would inevitably grow and spread and kill. Now they know that many — some say most or all — cancers can behave in a variety of ways. Clusters of abnormal cells like D.C.I.S. can sometimes disappear, stop growing or simply remain in place and never cause a problem. The suspicion is that the abnormal cells may be harmless and may not require treatment. But no one has done a rigorous study comparing outcomes for women who get treatment to those who get no treatment.
“The development of D.C.I.S. treatments and its handling over the past 40 years is an example of something we in medicine could have done better,” said Dr. Otis Brawley, chief medical officer for the American Cancer Society.