Gina Kolata, the medical writer for the New York Times, recently discussed the theory that the normal cells surrounding a neoplastic lesion and the body's immuno-surveillance system can play a critical role in a tumor's invasive potential (see: Old Ideas Spur New Approaches in Cancer Fight). I have always believed this to be the case but this theory is now being taken more seriously in the research community. She cites a number of research studies that support this argument. One passage from her article relating to the possible adverse consequences of diagnostic breast biopsies caught my attention. I quote it below:
[Dr. Kornelia Polyak of Harvard Medical School]thought [that] dangerous D.C.I.S. [ductal carcinoma in-situ] might have genes different from those of D.C.I.S. that remains harmlessly enclosed in milk ducts. Dangerous D.C.I.S. would look like invasive breast cancer cells and harmless D.C.I.S. would not. But, she found, D.C.I.S. cells looked just like cells from aggressive breast cancers — gene expression patterns, mutations and cell maturation patterns were all the same....“Why is it D.C.I.S. if it looks like invasive cancer?” She looked at cells surrounding D.C.I.S. The first thing she noticed was that when D.C.I.S. broke free of a milk duct, the duct’s outer layer had broken down. It could be that the duct falls apart because the cancer is bursting out. Or it could be that the cancer is escaping the duct because the outer layer disintegrated — which is what her research showed. As long as the milk duct is intact, D.C.I.S. cells cannot escape. She also found that when breast tissue is injured, wound healing can destroy the crucial outer layer of ducts, allowing D.C.I.S. to escape. That is what happens in animals, and it is her hypothesis that it happens in humans. It made her ask about biopsies. They are unavoidable, as she knows, because she recently had one herself. And they cannot be a huge factor in causing cancer or millions of women would be getting breast cancer at the site of their biopsies — and they are not. Still, she worries. “Frankly, this has not been studied extensively,” Dr. Polyak said. “People don’t like to bring it up.”
The question that is being asked above is whether a breast biopsy, initiated for the purpose of cancer diagnosis, can, in and of itself, promote the development of an invasive cancer on the basis of the inflammation and healing process that inexorably follows all biopsies. The basic idea is that these processes induce porosity of the basement membranes of breast ducts and enable the previously contained DCIS cells to escape into the surrounding tissue. Obviously, work will continue on this sequence of events to determine, first, whether this is a valid hypothesis and, second, whether the process can be blocked with, say, anti-inflammatory drugs. At the present time, breast biopsies are unavoidable because surgical pathology examination is the gold standard of breast diagnosis. However, in-situ techniques for the microscopic examination of tissue are rapidly being developed. Molecular imaging is also improving. All of these emerging diagnostic techniques may at some time be able to provide reliable diagnoses without disruption of the breast tissue.