Tissue microarrays: a practical guide

Tissue microarrays are a recent innovation in the field of pathology. They were originally designed as a high-throughput approach for researchers to assess the expression of interesting candidate disease-related genes or gene products simultaneously on hundreds of tissue samples. However, their use is becoming more widespread in routine pathology, for example for quality assurance and for the optimisation of diagnostic reagents such as monoclonal antibodies and gene probes. Several molecular and conventional pathological techniques can be performed on a single tissue array, thereby enabling morphology, DNA, RNA and protein targets to be analysed on sequential sections through multiple tissue samples. Moreover, compared with full-face tissue sections, tissue microarrays are a cost- and time-efficient, effective approach to analysing biomarker expression on a large number of samples. Whilst tissue microarrays are available from commercial sources, many pathology laboratories prefer to make in-house arrays from their often extensive pathology archive to facilitate the correlation of their findings with clinical parameters. The technical skills necessary to produce tissue arrays are well within the capacity of most laboratories. However, several pitfalls to successful array production exist. The present article describes the applications of this technique and details practical points for optimal tissue array production.