Laser Dissection Aids Pathologists, Patients

Susan M. Reiss

WASHINGTON -- Researchers battling cancer and other debilitating diseases will soon have a new weapon in their arsenal. A technique developed at the National Institutes of Health (NIH) will enable pathologists to assess the molecular behavior of just two to three cells -- information that can aid physicians in determining how best to treat individual patients.
Called laser capture microdissection, the technique holds two major advantages over current tissue-extraction methods. First, it eliminates the tedious, manual process of removing specimens from pathology slides and depositing them in test tubes. It can extract two cells within 8 s. Second, it preserves diseased lesions so pathologists can view the cells exactly as they appear in the patient.
Other tissue-extraction tools, such as flow cytometry, randomize the cells so viewing them exactly as they exist in a tumor is not possible.

Aggressive treatment possible
"If we can identify from a pathology slide certain red flags that signal aggressive cancer, for instance, then we can treat the patient aggressively," noted Robert Bonner, head of NIH's Biomedical Optics, Biomedical Engineering & Instrumentation Program. If the flags signal a less contentious cancer, then the patient can be treated with less invasive procedures. "In the end this technique may help how we treat people," he said.
The microdissection setup consists of a microscope, a CO₂ laser and thermoplastic film that acts as a coverslip. To extract cells, a pathologist locates the tissue of interest and presses a button. The laser, which is slightly more powerful than a laser pointer, heats the plastic, thereby immediately extracting the cells. Because the cells adhere to the film, scientists can either archive the specimen indefinitely or further manipulate it in real-time.
Simplicity was a driving force behind this system, said Michael Emmert-Buck, a National Cancer Institute scientist who worked on the project. "We were looking for the easiest, simplest way we could do this that fits with the way a pathologist is used to working," he said.
Currently pathologists rely on a microscope to locate the tissue to be isolated and then press a button that activates a camera.
The highly pure samples provide the most reliable indicators of why a cancer has spread or why a kidney has failed. The NIH scientists have extracted cells from kidney glomeruli, in situ breast cancer, atypical ductal hyperplasia of the breast, prostate neoplasia and lymphoid follicles. The team is developing a more sophisticated version that allows pathologists to dissect specimens with the aid of a computer screen.
The system should be available within the next year. The laser-capture-microdissection technique was described in Science, Nov. 8, 1996, Vol. 274, No. 5289, pp. 998-1001.