Laser capture microdissection in pathology

The molecular examination of pathologically altered cells and tissues at th e DNA, RNA, and protein level has revolutionised research and diagnostics i n pathology. However, the inherent heterogeneity of primary tissues with an admixture of various reactive cell populations can affect the outcome and interpretation of molecular studies. Recently, microdissection of tissue se ctions and cytological preparations has been used increasingly for the isol ation of homogeneous, morphologically identified cell populations, thus ove rcoming the obstacle of tissue complexity. In conjunction with sensitive an alytical techniques, such as the polymerase chain reaction, microdissection allows precise in vivo examination of cell populations, such as carcinoma in situ or the malignant cells of Hodgkin's disease, which are otherwise in accessible for conventional molecular studies. However, most microdissectio n techniques are very time consuming and require a high degree of manual de xterity, which limits their practical use. Laser capture microdissection (L CM), a novel technique developed at the National Cancer Institute, is an im portant advance in terms of speed, ease of use, and versatility of microdis section. LCM is based on the adherence of visually selected cells to a ther moplastic membrane, which overlies the dehydrated tissue section and is foc ally melted by triggering of a low energy infrared laser pulse. The melted membrane forms a composite with the selected tissue area, which can be remo ved by simple lifting of the membrane. LCM can be applied to a wide range o f cell and tissue preparations including paraffin wax embedded material. Th e use of immunohistochemical stains allows the selection of cells according to phenotypic and functional characteristics. Depending on the starting ma terial, DNA, good quality mRNA, and proteins can be extracted successfully from captured tissue fragments, down to the single cell level. In combinati on with techniques Like expression library construction, cDNA array hybridi sation and differential display, LCM will allow the establishment of "genet ic fingerprints" of specific pathological lesions, especially malignant neo plasms. In addition to the identification of new diagnostic and prognostic markers, this approach could help in establishing individualised treatments tailored to the molecular profile of a tumour. This review provides an ove rview of the technique of LCM, summarises current applications and new meth odical approaches, and tries to give a perspective on future developments. In addition, LCM is compared with other recently developed laser microdisse ction techniques.