In order to determine if there is cancer in the lymph nodes, pathologists must currently perform several  detailed, time-consuming tests. But University of Missouri researchers have developed a laser-induced ultrasound, called the photoacoustic method, that may help doctors locate the general area of the lymph node where melanoma cells are residing with much more efficiency than is currently possible. The new approach is detailed in the Journal of Biomedical Engineering.

In the photoacoustic method, a tabletop device scans a lymph node biopsy with laser pulses. About 95 percent of melanoma cells contain melanin, the pigment that gives skin its color, so they react to the laser's beam, absorbing the light. The laser causes the cells to heat and cool rapidly, which makes them expand and contract. This produces a popping noise that special sensors can detect. This method would examine the entire biopsy and identify the general area of the node that has cancer, giving pathologists a better idea of where to look for the cancer.

A researcher uses the photoacoustic method, a tabletop device scans a lymph node biopsy with laser pulses. This method could help doctors identify the stage of melanoma with more accuracy.

Photo Credit: Pinar Istek

In the study, researchers took human cancer cells and placed them inside canine lymph nodes. Then, using the laser, they determined the best ways to locate the cancer cells. The next step is to try the procedure using human lymph nodes.

"This method can be used to determine if the cancer has spread from stage 2, where the melanoma is still just in the skin lesion, to stage 3, where the melanoma has spread to the lymph nodes," said John Viator, assistant professor in the Department of Biological Engineering and Department of Dermatology. This technology could be an important tool in our fight against cancer."

Citation: McCormack et al., 'Photoacoustic Detection of Melanoma Micrometastasis in Sentinel Lymph Nodes', Journal of Biomedical Engineering, July 2009, 131(7), 074519; doi:10.1115/1.3169247