Faster Cancer Detection

Up to 16 years ago, cancer was detected by the crude method of waiting for an obvious malignancy to appear. Then Dr. George Papanicolaou of Cornell University Medical College devised his revolutionary method of early detection: smearing body secretions on glass slides for microscopic study of cells. In thousands of doctors' offices, the now standard Papanicolaou technique is to stain cells with polychrome dyes. Seen in the visible spectrum of light, the dyes readily emphasize the structure of malignant cells.

Last week an important speedup of this fast detection method was reported to a meeting of the International Academy of Pathology in Boston. Developed at Washington's Walter Reed Army Hospital, by Captain Leroy H. Dart Jr. and Master Sergeant Thomas R. Turner, the new wrinkle rests on facts about the cell's nucleic acids that were unknown in 1943. Biochemists are now sure that deoxyribonucleic acid (DNA) generally increases in human cancer cells; they suspect that ribonucleic acid (RNA) also rises. If the nucleic acid can be spotted under a microscope, it should be a tipoff to cancer.

To detect DNA and RNA, the Army team used acridine orange, a fluorochrome dye that easily unites with the nucleic acids and shines brightly under ultraviolet light. Result: the higher the cell's nucleic acid content, the more intense the fluorescence (green to yellow for DNA, red for RNA). After a few hours of training, a skilled cyto-technologist can spot malignant cells by the intensity of fluorescence he sees in his microscope.

Beauty of the technique is the exceptional clarity that acridine orange gives to a malignant cell: it glows sharply in a field of normal cells. When the Army team tested 4,995 cervical and vaginal smears with acridine orange, they detected 171 "suspicious" cases compared to 156 in a retest by the Papanicolaou technique. When they later did biopsies on nine of the 15 Papanicolaou "negatives," they found cancer in seven cases. This does not necessarily mean that the new method is more accurate. But it can definitely speed up cancer screening. At Walter Reed, cell-smear staining with acridine orange now takes twelve minutes, against half an hour with the Papanicolaou technique.

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