Procedure Determines if Growth Was Benign or Malignant : Results of Polyp Tests Due Today
BETHESDA, Md. — President Reagan and the world will know sometime today whether the two-inch-wide polyp removed from his colon on Saturday was benign or malignant, and if malignant, the likelihood that cancer cells may have spread to other organs.
The 48-hour delay in learning the answer is necessitated by the meticulous and time-consuming procedure that pathologists use to get the most accurate answers possible.
Among other things, this procedure involves soaking in formaldehyde for 24 hours the two-foot-long segment of colon that was removed along with the polyp, cutting it into sections, preparing perhaps hundreds of slides and examining them carefully under a microscope.
A much quicker answer could be obtained by freezing the tissues rather than soaking them in formaldehyde, but doctors say that method leaves more room for error in arriving at a diagnosis.
Lifelike Preservation
Aside from the fact that doctors do not consider the difference of a day or two to be important in cases such as this, the main reason for using the lengthier method is that it results in more lifelike preservation of the cells for viewing under the microscope.
The purpose of either freezing the specimens or soaking them in formaldehyde is to “fix” the cells as closely as possible in the state in which they existed in life. This is important because pathologists make their diagnoses on the basis of changes that are sometimes very subtle in the structure and architecture of the cells. Formaldehyde is preferred over freezing because the quality of the fixation is better.
“It’s like the differences you see if an animal that has frozen to death is put alongside an animal that has been beautifully preserved by a taxidermist,” said a Bethesda cancer surgeon who asked not to be identified by name.
The first thing that the pathologist does is to slice the entire segment of colon longitudinally with the polyp in the center, wash it out and pin it to a board. Both the lymph nodes and the blood vessels that are a part of the segment are also laid out. All of it is then soaked in the formaldehyde bath for 24 hours.
After rinsing in alcohol, certain parts of the segment are cut into blocks, which are sliced into thin cross-sections and mounted on slides.
Sections Carefully Studied
The pathologist is especially careful to examine closely the sections made from the entire polyp because it is possible that only a small piece is malignant. The two ends of the colon also are key elements if the polyp is found to be malignant. Any cancer cells at either end of the colon segment would indicate that the cancer may have spread beyond the segment to other tissues.
The presence of cancer cells in the lymph nodes or the blood vessels also would be considered indicative of spreading.
On Saturday, Dr. Steven Rosenberg, chief of cancer surgery at the National Cancer Institute, said that the chance of a polyp the size of the one removed from Reagan being malignant is “over 50%.”
