LASER-BEAM MICRODISSECTION IN THE DIAGNOSIS OF CUTANEOUS B-CELL LYMPHOMA

Interpretation of molecular analyses of cutaneous lymphoid infiltrates may be difficult because a heterogeneous group of cells is usually pr esent within the neoplasms. Extraction of DNA from tissue sections doe s not provide exact information about which cell population has been a nalysed. We present a laser microscope system that allows selective mo lecular analysis of single cells or small groups of cells in cases of cutaneous lymphoma. An ultraviolet (UV)-laser microscope system (PALM, Wolfratshausen, Germany) was used to isolate particular populations o f cells from a routinely processed specimen of a cutaneous follicular lymphoid proliferation. Using the UV-laser beam, a circle was cut arou nd a target germinal centre in order to separate it from neighbouring tissues and to isolate a pure population of germinal centre cells. Iso lated cells were scraped off with a micromanipulator and placed in a p roteinase-K solution. DNA was extracted and amplified by the polymeras e chain reaction (PCR) technique. Analysis of immunoglobulin J(H) gene rearrangement showed a distinct monoclonal band. In a second phase, u sing the same procedure in the same specimen, mantle zone cells around a germinal centre and single interfollicular B lymphocytes were isola ted for PCR analysis of immunoglobulin J(H) gene rearrangement. In thi s population of cells, no clonality could be detected. This new techni que allows the selective elimination of undesired cells and tissue fro m cutaneous neoplasms. By destruction of unwanted tissues with laser-b eam energy a contamination-free sample is obtained. Analysis of isolat ed cells in our case demonstrated a clonal rearrangement derived from germinal centre cells and not from other B lymphocytes in the specimen , confirming the diagnosis of cutaneous follicle centre lymphoma, The method described has exciting implications for dermatology and dermato pathology, allowing precise correlation of morphological features with findings by molecular genetics.