By Stephen Ornes
What Happens to a Donated Tumor?
Tissue banks may hold the key to cancer research, but can we overcome the obstacles to unlocking their full potential?
By Stephen Ornes
As investigators collect tumor samples for research, patients, patient advocates and legal experts will be wrangling over the issue of ownership in courts and biobanks for years to come. But ownership isn’t the only gray area. At a molecular level, the tumor begins to change as soon as a surgeon cuts off the blood supply.
A Ticking Clock
It’s easy to follow the path of a tumor through Yale–New Haven Hospital. In the operating room, the surgeon places the tissue into a sterile container. Someone takes it to the pathology department, one floor down and a few hallways away. The glass intake window at Yale’s pathology department, through which almost every bit of tissue removed at the hospital passes, looks like a fast-food drive-through window.
Beyond the window are bright rooms occupied by long steel tables, and researchers hunched over microscopes. Here, pathologists or pathologists’ assistants determine how much of the tissue is needed for diagnosis, how much can be preserved and how much can be used for research. For some types of cancer, like breast cancer, the tumors are usually small—which means very little can be used for research. A surgeon may need to get a diagnosis before completing surgery, in which case the tissue is quickly frozen and analyzed.
Larger samples from the tumor are fixed in formalin and embedded in paraffin, and other samples may be frozen (in liquid nitrogen, for example). In general, the fresh-frozen samples are the most sought-after for genetic research.
Physically tracking the location of a tumor is simple, but understanding what goes on inside the tissue between surgery and the fixation process is not. As soon as the surgeon cuts off the blood supply to the tumor, genetic material in the tissue starts to degrade, or break down at the molecular level.
The degradation continues as the tissue sits in the bucket, and as it is transported to pathology, and as it waits for a pathologist to get to it and freeze or fix it. The time between surgery and fixation is not standardized; it varies not only from institution to institution, but also from patient to patient within a single institution. A tumor may sit for minutes or hours. During this time, the tumor changes more rapidly than at any other time in its existence. In recent years, pathologists have become increasingly interested in these changes.
“The problem is, we don’t know what happens [to the tissue],” Rimm says. “If I look at a piece of tissue that had a one-hour time to fixation and compare it with a 10-minute time to fixation, there are variables in there that are very important to diagnostics.”